Allow darwin targets to use -framework CoreFoundation.

Bug: http://b/31245118
Change-Id: I5aa6162715b643af4a3073e6e403a6e1729f7c15
diff --git a/cc/config/x86_darwin_host.go b/cc/config/x86_darwin_host.go
index e89fc9c..1a4972e 100644
--- a/cc/config/x86_darwin_host.go
+++ b/cc/config/x86_darwin_host.go
@@ -91,14 +91,14 @@
 		"10.11",
 	}
 
-	darwinAvailableLibraries = addPrefix([]string{
+	darwinAvailableLibraries = append(addPrefix([]string{
 		"c",
 		"dl",
 		"m",
 		"ncurses",
 		"pthread",
 		"z",
-	}, "-l")
+	}, "-l"), "-framework CoreFoundation")
 )
 
 const (