Index: llvm/trunk/utils/gn/build/toolchain/BUILD.gn
===================================================================
--- llvm/trunk/utils/gn/build/toolchain/BUILD.gn
+++ llvm/trunk/utils/gn/build/toolchain/BUILD.gn
@@ -157,13 +157,17 @@
     cc = "bin/clang"
     cxx = "bin/clang++"
     ld = cxx
-    ar = "bin/llvm-ar"
+    if (current_os != "mac") {
+      ar = "bin/llvm-ar"
+    }
 
     deps = [
       "//:clang($host_toolchain)",
       "//:lld($host_toolchain)",
-      "//:llvm-ar($host_toolchain)",
     ]
+    if (current_os != "mac") {
+      deps += [ "//:llvm-ar($host_toolchain)" ]
+    }
   }
 }
 
Index: llvm/trunk/utils/gn/secondary/BUILD.gn
===================================================================
--- llvm/trunk/utils/gn/secondary/BUILD.gn
+++ llvm/trunk/utils/gn/secondary/BUILD.gn
@@ -5,10 +5,12 @@
 group("default") {
   deps = [
     "//clang/test",
-    "//compiler-rt/test/hwasan",
     "//lld/test",
     "//llvm/test",
   ]
+  if (current_os == "linux" || current_os == "android") {
+    deps += [ "//compiler-rt/test/hwasan" ]
+  }
 
   testonly = true
 }