fmt.Fprintf(h, "CC=%q %q %q %q\n", ccExe, cppflags, cflags, ldflags)
		// Include the C compiler tool ID so that if the C
		// compiler changes we rebuild the package.
		if ccID, _, err := b.gccToolID(ccExe[0], "c"); err == nil {
			fmt.Fprintf(h, "CC ID=%q\n", ccID)
		}
		if len(p.CXXFiles)+len(p.SwigCXXFiles) > 0 {
			cxxExe := b.cxxExe()
			fmt.Fprintf(h, "CXX=%q %q\n", cxxExe, cxxflags)