[WIP] rustc_target: Remove crt_static_respected and crt_static_allows_dylibs

[petrochenkov]

Always respect +crt-static option if user passed it.
If the user wants to link to e.g. bionic or glibc statically, rustc should at least not stay in the way.

Linking to libc statically may require linking some startup files as well or passing extra linker options.
For some targets like *-musl rustc supports doing it implicitly.
For other targets it's responsibility of the user passing +crt-static to link them using -C (pre-)link-args and similar flags.

cc rust-lang/libc#1711 #40113 #70095

[rust-highfive]

r? @cramertj

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[petrochenkov]

For some background: I needed to produce some library usable in a restricted environment requiring no dynamically linked libc (a binary instrumentation system), this is an issue I immediately encountered when attempting to do it in Rust instead of C/C++.

[rust-highfive]

The job x86_64-gnu-llvm-7 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2020-03-28T15:45:54.2958349Z ========================== Starting Command Output ===========================
2020-03-28T15:45:54.2961704Z [command]/bin/bash --noprofile --norc /home/vsts/work/_temp/a5906e84-27bd-4590-a331-76e566dc2a15.sh
2020-03-28T15:45:54.2961987Z 
2020-03-28T15:45:54.2967006Z ##[section]Finishing: Disable git automatic line ending conversion
2020-03-28T15:45:54.2987837Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/70501/merge to s
2020-03-28T15:45:54.2991784Z Task         : Get sources
2020-03-28T15:45:54.2992097Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-03-28T15:45:54.2992415Z Version      : 1.0.0
2020-03-28T15:45:54.2992620Z Author       : Microsoft
---
2020-03-28T15:45:55.2853711Z ##[command]git remote add origin https://github.com/rust-lang/rust
2020-03-28T15:45:55.2860808Z ##[command]git config gc.auto 0
2020-03-28T15:45:55.2864537Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2020-03-28T15:45:55.2867855Z ##[command]git config --get-all http.proxy
2020-03-28T15:45:55.2874172Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/70501/merge:refs/remotes/pull/70501/merge
---
2020-03-28T15:54:12.6240823Z    Compiling rustc_feature v0.0.0 (/checkout/src/librustc_feature)
2020-03-28T15:54:14.1436583Z    Compiling fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
2020-03-28T15:54:15.7563061Z    Compiling rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
2020-03-28T15:54:16.4733438Z    Compiling rustc_hir v0.0.0 (/checkout/src/librustc_hir)
2020-03-28T15:54:25.5478090Z    Compiling rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
2020-03-28T15:54:27.6822426Z    Compiling rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
2020-03-28T15:54:32.0757383Z    Compiling rustc_attr v0.0.0 (/checkout/src/librustc_attr)
2020-03-28T15:54:36.2274027Z    Compiling rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
2020-03-28T15:55:06.7529806Z    Compiling rustc_parse v0.0.0 (/checkout/src/librustc_parse)
---
2020-03-28T16:16:31.6034001Z    Compiling rustc_feature v0.0.0 (/checkout/src/librustc_feature)
2020-03-28T16:16:33.4137083Z    Compiling fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
2020-03-28T16:16:35.5554110Z    Compiling rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
2020-03-28T16:16:35.9944976Z    Compiling rustc_hir v0.0.0 (/checkout/src/librustc_hir)
2020-03-28T16:16:47.5274322Z    Compiling rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
2020-03-28T16:16:49.6932393Z    Compiling rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
2020-03-28T16:16:55.3985553Z    Compiling rustc_attr v0.0.0 (/checkout/src/librustc_attr)
2020-03-28T16:17:00.1514475Z    Compiling rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
2020-03-28T16:17:39.3845305Z    Compiling rustc_parse v0.0.0 (/checkout/src/librustc_parse)
---
2020-03-28T16:42:31.9357659Z .................................................................................................... 1700/9855
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---
2020-03-28T16:53:43.3641856Z .......................................................
2020-03-28T16:53:43.3644370Z failures:
2020-03-28T16:53:43.3644828Z 
2020-03-28T16:53:43.3645777Z ---- [ui] ui/crt-static-on-works.rs stdout ----
2020-03-28T16:53:43.3647177Z thread '[ui] ui/crt-static-on-works.rs' panicked at 'failed to exec `"/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/crt-static-on-works/a"`: Os { code: 2, kind: NotFound, message: "No such file or directory" }', src/tools/compiletest/src/runtest.rs:1824:25
2020-03-28T16:53:43.3648662Z 
2020-03-28T16:53:43.3648789Z 
2020-03-28T16:53:43.3648963Z failures:
2020-03-28T16:53:43.3649494Z     [ui] ui/crt-static-on-works.rs
2020-03-28T16:53:43.3649494Z     [ui] ui/crt-static-on-works.rs
2020-03-28T16:53:43.3650985Z 
2020-03-28T16:53:43.3652108Z test result: FAILED. 9794 passed; 1 failed; 60 ignored; 0 measured; 0 filtered out
2020-03-28T16:53:43.3652603Z 
2020-03-28T16:53:43.3709348Z thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:348:22
2020-03-28T16:53:43.3729660Z 
2020-03-28T16:53:43.3729832Z 
2020-03-28T16:53:43.3733559Z command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-7/bin/FileCheck" "--nodejs" "/usr/bin/node" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "7.0.0" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
2020-03-28T16:53:43.3736009Z 
2020-03-28T16:53:43.3736117Z 
2020-03-28T16:53:43.3740338Z failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test --exclude src/tools/tidy
2020-03-28T16:53:43.3740916Z Build completed unsuccessfully in 1:02:59
2020-03-28T16:53:43.3740916Z Build completed unsuccessfully in 1:02:59
2020-03-28T16:53:43.3785158Z == clock drift check ==
2020-03-28T16:53:43.3807637Z   local time: Sat Mar 28 16:53:43 UTC 2020
2020-03-28T16:53:43.5425761Z   network time: Sat, 28 Mar 2020 16:53:43 GMT
2020-03-28T16:53:43.5430201Z == end clock drift check ==
2020-03-28T16:53:43.9767712Z 
2020-03-28T16:53:43.9852413Z ##[error]Bash exited with code '1'.
2020-03-28T16:53:43.9867129Z ##[section]Finishing: Run build
2020-03-28T16:53:43.9932448Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/70501/merge to s
2020-03-28T16:53:43.9937699Z Task         : Get sources
2020-03-28T16:53:43.9938046Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-03-28T16:53:43.9938384Z Version      : 1.0.0
2020-03-28T16:53:43.9938614Z Author       : Microsoft
2020-03-28T16:53:43.9938614Z Author       : Microsoft
2020-03-28T16:53:43.9938966Z Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
2020-03-28T16:53:43.9939387Z ==============================================================================
2020-03-28T16:53:44.3205504Z Cleaning any cached credential from repository: rust-lang/rust (GitHub)
2020-03-28T16:53:44.3253741Z ##[section]Finishing: Checkout rust-lang/rust@refs/pull/70501/merge to s
2020-03-28T16:53:44.3345827Z Cleaning up task key
2020-03-28T16:53:44.3347221Z Start cleaning up orphan processes.
2020-03-28T16:53:44.3524311Z Terminate orphan process: pid (4899) (python)
2020-03-28T16:53:44.3688151Z ##[section]Finishing: Finalize Job

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[petrochenkov]

Linking to libc statically may require linking some startup files as well or passing extra linker options.
... it's responsibility of the user passing +crt-static to link them using -C (pre-)link-args and similar flags.

Hmm, this setup may break though if rustc starts passing the begin and end objects implicitly for the given target in the future.
Perhaps we should use feature gate errors when +crt-static is used for non-whitelisted targets.

[petrochenkov]

I don't have resources to pursue this, unfortunately, and I needed this yesterday rather than in few months in the future.

The workaround is to produce a staticlib and then link with whatever necessary manually.