func os/exec.dedupEnvCase

2 uses

	os/exec (current package)
		exec.go#L1244: 	return dedupEnvCase(runtime.GOOS == "windows", runtime.GOOS == "plan9", env)
		exec.go#L1250: func dedupEnvCase(caseInsensitive, nulOK bool, env []string) ([]string, error) {