-extld option to set the host linker to the C++ compiler.

These defaults mean that Go-aware build systems can ignore the linking
changes and keep running plain 'cmd/link' and get reasonable results, but
they can also control the linking details if desired.

		log.Printf("%s: contains CRLFs", filename)
		exitCode = 1
	}
	if filepath.Base(filename) == "go1.4.txt" {
		// No use for blank lines in api files, except go1.4.txt
		// used them in a reasonable way and we should let it be.
	} else if strings.HasPrefix(s, "\n") || strings.Contains(s, "\n\n") {
		log.Printf("%s: contains a blank line", filename)
		exitCode = 1
	}
	if s == "" {