Migrate run-make/rustdoc-shared-flags to rmake

src/tools/tidy/src/allowed_run_make_makefiles.txt

@@ -50,7 +50,6 @@ run-make/duplicate-output-flavors/Makefile
 run-make/dylib-chain/Makefile
 run-make/emit-named-files/Makefile
 run-make/emit-path-unhashed/Makefile
-run-make/emit-shared-files/Makefile
 run-make/emit-stack-sizes/Makefile
 run-make/emit-to-stdout/Makefile
 run-make/emit/Makefile

tests/run-make/rustdoc-shared-flags/rmake.rs

@@ -0,0 +1,17 @@
+// Assert that the search index is generated deterministically, regardless of the
+// order that crates are documented in.
+
+use run_make_support::{Diff, rustc, rustdoc};
+
+fn compare_outputs(args: &[&str]) {
+    let rustc_output = String::from_utf8(rustc().args(args).command_output().stdout).unwrap();
+    let rustdoc_output = String::from_utf8(rustdoc().args(args).command_output().stdout).unwrap();
+
+    Diff::new().expected_text("rustc", rustc_output).actual_text("rustdoc", rustdoc_output).run();
+}
+
+fn main() {
+    compare_outputs(&["-C", "help"]);
+    compare_outputs(&["-Z", "help"]);
+    compare_outputs(&["-C", "passes=list"]);
+}