}

	cmdArgs = append(cmdArgs, "-x", "c", "-", "-o", tmp)

	if cfg.BuildN {
		sh.ShowCmd(b.WorkDir, "%s || true", joinUnambiguously(cmdArgs))
		return false
	}

	// gccCompilerID acquires b.exec, so do before acquiring lock.
	compilerID, cacheOK := b.gccCompilerID(compiler[0])

	b.exec.Lock()
	defer b.exec.Unlock()
	if b, ok := b.flagCache[key]; ok {
		return b
	}