The remap-debuginfo config option remaps paths in most crates, but it
does not apply to proc-macros, so they are still non-reproducible.
This patch fixes that.

The modules are now populated implicitly on the first access

Move some code into `build_reduced_graph.rs` to keep `BuildReducedGraphVisitor` it private
Also move the def collector call to `build_reduced_graph.rs`, it belongs there.

resolve: Populate external modules in more automatic and lazy way

So, resolve had this function `populate_module_if_necessary` for loading module children from other crates from metadata.
I never really understood when it should've been called and when not.
This PR removes the function and loads the module children automatically on the first access instead.

r? @eddyb

Feature gate 'yield $expr?' pre-expansion

Also improve the overall ergonomics of pre-expansion gating in general.

r? @Zoxc

…chton

Update rustc-demangle to 0.1.16.

Includes rust-lang/rustc-demangle#29 and rust-lang/rustc-demangle#30.
You can see the effects of the former in the testcase changes.

r? @alexcrichton cc @davidtwco @michaelwoerister

Remap paths for proc-macro crates.

The remap-debuginfo config option remaps paths in most crates, but it does not apply to proc-macros, so they are still non-reproducible.  This patch fixes that.

I'm not completely sure if this is the best way to do this, but to get reproducible builds we need librustc_macros to be built with --remap-path-prefix.  I was previously modifying Cargo to pass that argument to all child crates, so this seems simpler and more correct.

I did not add a test since there do not seem to be any existing tests for RUSTC_DEBUGINFO_MAP.

r? @alexcrichton

add git keyword to submodule comments in config.example.toml

I searched over config.example.toml file looking for a place to disable git submodules from being updated, and missed the two options related to this because they did not include the keyword git. This pr simply adds git to the relevant comments so hopefully others won't also miss that these options exist.

…mulacrum

Rename overflowing_{add,sub,mul} intrinsics to wrapping_{add,sub,mul}.

These confused @Gankra, and then, also me, especially since `overflowing_*` *methods* also exist, but they map to `*_with_overflow` intrinsics!

r? @oli-obk / @nikomatsakis cc @Mark-Simulacrum (on the rustbuild workaround)