[gn build] Embed __TEXT __info_plist section into clang binary on macOS

[thakis]

Summary

Verified by comparing the output of otool -P bin/clang between the GN and the CMake build.

[phosek]

LGTM

llvm/trunk/utils/gn/secondary/clang/tools/driver/BUILD.gn

 import("//llvm/utils/gn/build/symlink_or_copy.gni")
+import("//llvm/version.gni")
 
 symlinks = [
   # target_name, symlink_target pairs: GN doesn't support '+' in rule names.
   [
     "clangxx",
     "clang++",
   ],
   [

 # //:clang depends on this symlink target, see comment in //BUILD.gn.
 group("symlinks") {
   deps = []
   foreach(target, symlinks) {
     deps += [ ":${target[0]}" ]
   }
 }
 
+if (host_os == "mac") {
+  action("write_info_plist") {
+    script = "//llvm/utils/gn/build/write_cmake_config.py"
+    sources = [
+      "Info.plist.in",
+    ]
+    outputs = [
+      "$target_gen_dir/Info.plist",
+    ]
+
+    args = [
+      "-o",
+      rebase_path(outputs[0], root_out_dir),
+      rebase_path(sources[0], root_out_dir),
+
+      "TOOL_INFO_BUILD_VERSION=$llvm_version_major.$llvm_version_minor",
+      "TOOL_INFO_NAME=clang",
+      "TOOL_INFO_UTI=org.llvm.clang",
+      "TOOL_INFO_VERSION=$llvm_version",
+    ]
+  }
+}
+
 executable("clang") {
   configs += [ "//llvm/utils/gn/build:clang_code" ]
   deps = [
     "//clang/include/clang/Config",
     "//clang/lib/Basic",
     "//clang/lib/CodeGen",
     "//clang/lib/Driver",
     "//clang/lib/Frontend",
deps = [
     "//llvm/lib/Transforms/IPO",
     "//llvm/lib/Transforms/InstCombine",
     "//llvm/lib/Transforms/Instrumentation",
     "//llvm/lib/Transforms/ObjCARC",
     "//llvm/lib/Transforms/Scalar",
     "//llvm/lib/Transforms/Utils",
     "//llvm/lib/Transforms/Vectorize",
   ]
+  if (host_os == "mac") {
+    deps += [ ":write_info_plist" ]
+    plist = get_target_outputs(":write_info_plist")
+    ldflags = [ "-Wl,-sectcreate,__TEXT,__info_plist," +
+                rebase_path(plist[0], root_out_dir) ]
+  }
   sources = [
     "cc1_main.cpp",
     "cc1as_main.cpp",
     "cc1gen_reproducer_main.cpp",
     "driver.cpp",
   ]
-
-  # FIXME: Info.plist embedding for mac builds.
 }