Skip adding -lstatic to libtest and libstd on Darwin (bazelbuild#1620)

This is one way to fix bazelbuild#1573, which I have a feeling can be wrong. The binaries produced with this patch contain all required symbols and are working fine on macOS.

Author: gferon

rust/private/rustc.bzl

@@ -1668,7 +1668,7 @@ def _get_crate_dirname(crate):
     """
     return crate.output.dirname
 
-def _portable_link_flags(lib, use_pic, ambiguous_libs, get_lib_name, for_windows):
+def _portable_link_flags(lib, use_pic, ambiguous_libs, get_lib_name, for_windows = False, for_darwin = False):
     artifact = get_preferred_artifact(lib, use_pic)
     if ambiguous_libs and artifact.path in ambiguous_libs:
         artifact = ambiguous_libs[artifact.path]
@@ -1706,7 +1706,7 @@ def _portable_link_flags(lib, use_pic, ambiguous_libs, get_lib_name, for_windows
             artifact.basename.startswith("libtest-") or artifact.basename.startswith("libstd-") or
             artifact.basename.startswith("test-") or artifact.basename.startswith("std-")
         ):
-            return ["-lstatic=%s" % get_lib_name(artifact)]
+            return [] if for_darwin else ["-lstatic=%s" % get_lib_name(artifact)]
         return [
             "-lstatic=%s" % get_lib_name(artifact),
             "-Clink-arg=-l%s" % (get_lib_name(artifact) if not for_windows else artifact.basename),
@@ -1738,7 +1738,7 @@ def _make_link_flags_darwin(linker_input_and_use_pic_and_ambiguous_libs):
                 ("link-arg=-Wl,-force_load,%s" % get_preferred_artifact(lib, use_pic).path),
             ])
         else:
-            ret.extend(_portable_link_flags(lib, use_pic, ambiguous_libs, get_lib_name_default, for_windows = False))
+            ret.extend(_portable_link_flags(lib, use_pic, ambiguous_libs, get_lib_name_default, for_darwin = True))
     return ret
 
 def _make_link_flags_default(linker_input_and_use_pic_and_ambiguous_libs):
@@ -1755,7 +1755,7 @@ def _make_link_flags_default(linker_input_and_use_pic_and_ambiguous_libs):
                 "link-arg=-Wl,--no-whole-archive",
             ])
         else:
-            ret.extend(_portable_link_flags(lib, use_pic, ambiguous_libs, get_lib_name_default, for_windows = False))
+            ret.extend(_portable_link_flags(lib, use_pic, ambiguous_libs, get_lib_name_default))
     return ret
 
 def _libraries_dirnames(linker_input_and_use_pic_and_ambiguous_libs):

test/portable_link_flags_darwin/BUILD.bazel

@@ -0,0 +1,31 @@
+load("@rules_cc//cc:defs.bzl", "cc_library")
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_library")
+
+rust_library(
+    name = "rust-lib",
+    srcs = ["lib.rs"],
+    edition = "2021",
+)
+
+cc_library(
+    name = "c-lib",
+    srcs = ["api.c"],
+    deps = [":rust-lib"],
+)
+
+rust_binary(
+    name = "app",
+    srcs = ["main.rs"],
+    edition = "2021",
+    deps = [":c-lib"],
+)
+
+sh_test(
+    name = "test",
+    srcs = ["test.sh"],
+    args = ["$(location :app)"],
+    data = [":app"],
+    target_compatible_with = [
+        "@platforms//os:macos",
+    ],
+)

test/portable_link_flags_darwin/api.c

@@ -0,0 +1,5 @@
+#include <stdio.h>
+
+void lib() {
+    printf("Hello, C lib!");
+}

test/portable_link_flags_darwin/lib.rs

@@ -0,0 +1,3 @@
+pub fn lib() {
+    println!("Hello, Rust lib!");
+}

test/portable_link_flags_darwin/main.rs

@@ -0,0 +1 @@
+fn main() {}

test/portable_link_flags_darwin/test.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+set -e
+
+if otool -L $1 | grep -q libtest; then
+    echo "error: rust_binary is dynamically linked against libtest!"
+    exit 1
+fi
+
+if otool -L $1 | grep -q libstd; then
+    echo "error: rust_binary is dynamically linked against libstd!"
+    exit 1
+fi