Implement -Zlink-native-libraries

src/librustc_codegen_ssa/back/link.rs

@@ -1379,10 +1379,17 @@ fn link_args<'a, B: ArchiveBuilder<'a>>(
     // link line. And finally upstream native libraries can't depend on anything
     // in this DAG so far because they're only dylibs and dylibs can only depend
     // on other dylibs (e.g., other native deps).
-    add_local_native_libraries(cmd, sess, codegen_results);
+    //
+    // If -Zlink-native-libraries=false is set, then the assumption is that an
+    // external build system already has the native dependencies defined, and it
+    // will provide them to the linker itself.
+    if sess.opts.debugging_opts.link_native_libraries.unwrap_or(true) {
+        add_local_native_libraries(cmd, sess, codegen_results);
+    }
     add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
-    add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
-
+    if sess.opts.debugging_opts.link_native_libraries.unwrap_or(true) {
+        add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
+    }
     // Tell the linker what we're doing.
     if crate_type != config::CrateType::Executable {
         cmd.build_dylib(out_filename);

src/librustc_session/options.rs

@@ -959,4 +959,6 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "link the `.rlink` file generated by `-Z no-link`"),
     new_llvm_pass_manager: Option<bool> = (None, parse_opt_bool, [TRACKED],
         "use new LLVM pass manager"),
+    link_native_libraries: Option<bool> = (None, parse_opt_bool, [UNTRACKED],
+        "Link native libraries in the linker invocation."),
 }

src/test/ui/issues/issue-70093.rs

@@ -0,0 +1,8 @@
+// run-pass
+// compile-flags: -Zlink-native-libraries=no -Cdefault-linker-libraries=yes
+// ignore-windows - this will probably only work on unixish systems
+
+#[link(name = "some-random-non-existent-library", kind = "static")]
+extern "C" {}
+
+fn main() {}