--- build/moz.configure/toolchain.configure.orig
+++ build/moz.configure/toolchain.configure
@@ -95,7 +95,7 @@
         sdk_min_version = Version("10.12")
 
         if sdk:
-            sdk = sdk[0]
+            return sdk[0]
         elif host.os == "OSX":
             sdk = check_cmd_output(
                 "xcrun", "--show-sdk-path", onerror=lambda: ""
