fix(layout): Remove hashes from bins in new layout

There is a desire in #8332 to make our use of `-Cextra-file-name` in `deps/` more
consistent across platforms.
Having it present gets in the way of finding PDBs.
With #15010, we no longer need `-Cextra-file-name` to avoid collisions.
It might still be used by rustc for faster lookups though.
So we can at least adjust all other platforms to be like Windows,
making things consistent

Addresses #8332 if #15010 is stabilized

Part of #15010

Author: epage

src/cargo/core/compiler/build_runner/compilation_files.rs

@@ -887,7 +887,29 @@ fn use_extra_filename(bcx: &BuildContext<'_, '_>, unit: &Unit) -> bool {
         // Doc tests do not have metadata.
         return false;
     }
-    {
+    if bcx.gctx.cli_unstable().build_dir_new_layout {
+        if unit.mode.is_any_test() || unit.mode.is_check() {
+            // These always use metadata.
+            return true;
+        }
+        // No metadata in these cases:
+        //
+        // - dylib, cdylib, executable: `pkg_dir` avoids collisions for us and rustc isn't looking these
+        //   up by `-Cextra-filename`
+        //
+        // The __CARGO_DEFAULT_LIB_METADATA env var is used to override this to
+        // force metadata in the hash. This is only used for building libstd. For
+        // example, if libstd is placed in a common location, we don't want a file
+        // named /usr/lib/libstd.so which could conflict with other rustc
+        // installs. In addition it prevents accidentally loading a libstd of a
+        // different compiler at runtime.
+        // See https://github.com/rust-lang/cargo/issues/3005
+        if (unit.target.is_dylib() || unit.target.is_cdylib() || unit.target.is_executable())
+            && bcx.gctx.get_env("__CARGO_DEFAULT_LIB_METADATA").is_err()
+        {
+            return false;
+        }
+    } else {
         if unit.mode.is_any_test() || unit.mode.is_check() {
             // These always use metadata.
             return true;

tests/testsuite/build_dir.rs

@@ -336,10 +336,10 @@ fn cargo_tmpdir_should_output_to_build_dir() {
 [ROOT]/foo/build-dir/CACHEDIR.TAG
 [ROOT]/foo/build-dir/debug/.cargo-lock
 [ROOT]/foo/build-dir/debug/build/foo/[HASH]/deps/foo-[HASH].d
-[ROOT]/foo/build-dir/debug/build/foo/[HASH]/deps/foo-[HASH].d
+[ROOT]/foo/build-dir/debug/build/foo/[HASH]/deps/foo.d
 [ROOT]/foo/build-dir/debug/build/foo/[HASH]/deps/foo[..].d
 [ROOT]/foo/build-dir/debug/build/foo/[HASH]/deps/foo-[HASH][EXE]
-[ROOT]/foo/build-dir/debug/build/foo/[HASH]/deps/foo-[HASH][EXE]
+[ROOT]/foo/build-dir/debug/build/foo/[HASH]/deps/foo[EXE]
 [ROOT]/foo/build-dir/debug/build/foo/[HASH]/deps/foo[..][EXE]
 [ROOT]/foo/build-dir/debug/build/foo/[HASH]/fingerprint/invoked.timestamp
 [ROOT]/foo/build-dir/debug/build/foo/[HASH]/fingerprint/dep-test-bin-foo

tests/testsuite/clean_new_layout.rs

@@ -126,7 +126,7 @@ fn clean_multiple_packages_in_glob_char_path() {
     let foo_path = &p.build_dir().join("debug").join("build");
 
     #[cfg(not(target_env = "msvc"))]
-    let file_glob = "foo/*/deps/foo-*";
+    let file_glob = "foo/*/deps/foo*";
 
     #[cfg(target_env = "msvc")]
     let file_glob = "foo/*/deps/foo.pdb";