Fix script and compiler invocation when using non-default toolchain.

build/config/mac/base_rules.gni

Index: build/config/mac/base_rules.gni
diff --git a/build/config/mac/base_rules.gni b/build/config/mac/base_rules.gni
index 76610cc2d2210e5406fd34c6c9844e167ab055b0..109710dd3f77c4456cdac93bb7b49bf03dd76e96 100644
--- a/build/config/mac/base_rules.gni
+++ b/build/config/mac/base_rules.gni
@@ -49,8 +49,8 @@ template("convert_plist") {
       "-convert",
       invoker.format,
       "-o",
-      rebase_path(invoker.output, root_out_dir),
-      rebase_path(invoker.source, root_out_dir),
+      rebase_path(invoker.output, root_build_dir),
+      rebase_path(invoker.source, root_build_dir),
     ]
   }
 }
@@ -270,7 +270,7 @@ template("framework_bundle") {
     # TODO(sdefresne): should we have a framework_dirs similar to lib_dirs
     # and include_dirs to avoid duplicate values on the command-line.
     visibility = [ ":$_framework_target" ]
-    ldflags = [ "-F" + rebase_path("$root_out_dir/.", root_out_dir) ]
+    ldflags = [ "-F" + rebase_path("$root_out_dir/.", root_build_dir) ]
     lib_dirs = [ root_out_dir ]
     libs = [ _framework_name ]
   }