Allow linking against SystemConfiguration framework on Mac

This is needed for Python

Test: m py2-cmd; py2-cmd -murllib
Change-Id: I156bd281cb341eba7bdd7e7a15b87e8e90ecee1d
diff --git a/cc/config/x86_darwin_host.go b/cc/config/x86_darwin_host.go
index 09632db..1026370 100644
--- a/cc/config/x86_darwin_host.go
+++ b/cc/config/x86_darwin_host.go
@@ -79,6 +79,7 @@
 		"-framework Foundation",
 		"-framework IOKit",
 		"-framework Security",
+		"-framework SystemConfiguration",
 	)
 )