Always use the standard OSX SDK tools

Instead of whatever happens to be in PATH.

Test: port install gcc5; attempt to build host binaries
Change-Id: If4af32596edd6fd3e459c3d574ab0ff495f236ff
diff --git a/cc/makevars.go b/cc/makevars.go
index e4d8fe6..200faff 100644
--- a/cc/makevars.go
+++ b/cc/makevars.go
@@ -16,7 +16,6 @@
 
 import (
 	"fmt"
-	"path/filepath"
 	"sort"
 	"strings"
 
@@ -186,9 +185,7 @@
 	if toolchain.ClangSupported() {
 		clangPrefix := secondPrefix + "CLANG_" + typePrefix
 		clangExtras := "-target " + toolchain.ClangTriple()
-		if target.Os != android.Darwin {
-			clangExtras += " -B" + filepath.Join(toolchain.GccRoot(), toolchain.GccTriple(), "bin")
-		}
+		clangExtras += " -B" + config.ToolPath(toolchain)
 
 		ctx.Strict(clangPrefix+"GLOBAL_CFLAGS", strings.Join([]string{
 			toolchain.ClangCflags(),