Use LLVM archiver on macOS

macOS libtool doesn't seem to handle LTO object files, use LLVM linker
instead to avoid the error.

Change-Id: I4a5dd0ee8eb508b86ec2a9431b09f69b8b9d5eb1
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/4600
Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: Petr Hosek <phosek@google.com>

build/build_mac.ninja.template

diff --git a/build/build_mac.ninja.template b/build/build_mac.ninja.template
index ff82eb8..e7dedac 100644
--- a/build/build_mac.ninja.template
+++ b/build/build_mac.ninja.template
@@ -11,7 +11,7 @@
   deps = gcc
 
 rule alink_thin
-  command = rm -f $out && libtool -static -o $out $in
+  command = rm -f $out && $ar rcs $out $in
   description = AR $out
 
 rule link