p := a.Package
	sh := b.Shell(a)
	if pcargs := p.CgoPkgConfig; len(pcargs) > 0 {
		// pkg-config permits arguments to appear anywhere in
		// the command line. Move them all to the front, before --.
		var pcflags []string
		var pkgs []string
		for _, pcarg := range pcargs {
			if pcarg == "--" {
				// We're going to add our own "--" argument.