Don't use -B...gcc.. on Darwin

We don't ship binutils on Darwin, so there is no point in telling clang
to look in that path. (The path being used doesn't even exist). This
matches the Make behavior.

Change-Id: I663047057ff8df8a349483532da8018af13d50d8
diff --git a/cc/cc.go b/cc/cc.go
index d2f0930..0c47c79 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -1091,7 +1091,10 @@
 		flags.LdFlags = clangFilterUnknownCflags(flags.LdFlags)
 
 		target := "-target " + toolchain.ClangTriple()
-		gccPrefix := "-B" + filepath.Join(toolchain.GccRoot(), toolchain.GccTriple(), "bin")
+		var gccPrefix string
+		if !ctx.Darwin() {
+			gccPrefix = "-B" + filepath.Join(toolchain.GccRoot(), toolchain.GccTriple(), "bin")
+		}
 
 		flags.CFlags = append(flags.CFlags, target, gccPrefix)
 		flags.AsFlags = append(flags.AsFlags, target, gccPrefix)
diff --git a/cc/makevars.go b/cc/makevars.go
index 247036e..91ba748 100644
--- a/cc/makevars.go
+++ b/cc/makevars.go
@@ -86,7 +86,10 @@
 
 	if toolchain.ClangSupported() {
 		clangPrefix := secondPrefix + "CLANG_" + typePrefix
-		clangExtras := "-target " + toolchain.ClangTriple() + " -B" + filepath.Join(toolchain.GccRoot(), toolchain.GccTriple(), "bin")
+		clangExtras := "-target " + toolchain.ClangTriple()
+		if ht != common.Darwin {
+			clangExtras += " -B" + filepath.Join(toolchain.GccRoot(), toolchain.GccTriple(), "bin")
+		}
 
 		globalClangCflags := fmt.Sprintf("${commonClangGlobalCflags} ${clangExtraCflags} ${%sClangGlobalCflags}", hod)