cmd/go, cmd/link: use Windows response files for gcc/g++ to avoid arg length limits

What version of Go are you using (go version)?

1.11.1

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

windows 386/amd64

What did you do?

Tried to compile a cgo program.

package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
)

func main() {
	testCgo("c")
	testCgo("cpp")
}

func testCgo(ending string) {
	tmpdir, _ := ioutil.TempDir("", "cgo_resp_issue")
	defer os.RemoveAll(tmpdir)

	ioutil.WriteFile(filepath.Join(tmpdir, "gofile.go"), []byte(fmt.Sprint("package main\nimport \"C\"\nfunc main(){}")), 0644)
	for i := 0; i < 1000; i++ {
		ioutil.WriteFile(filepath.Join(tmpdir, fmt.Sprintf("cfile_%v."+ending, i)), []byte(fmt.Sprintf("void func_%v(){}", i)), 0644)
	}

	cmd := exec.Command("go", "build", "-v", "-x", "-ldflags=all=\"-extldflags=-v\"")
	cmd.Dir = tmpdir
	if out, err := cmd.CombinedOutput(); err != nil {
		println("failed:", ending, err.Error(), string(out))
	}
}

What did you expect to see?

a successful compilation

What did you see instead?

gcc: error: CreateProcess: No such file or directory and/or g++: error: CreateProcess: No such file or directory

Possible solution?

This patch works for my needs. It's mostly a copy of: https://go-review.googlesource.com/c/go/+/110395 But I also needed to escape the backslashes to make it work.

[patch omitted]

More info

The issue is related to: https://github.com/golang/go/issues/18468 and https://github.com/golang/go/blob/master/src/cmd/go/internal/work/exec.go#L2851

The problem is caused by the 32K character limit on windows https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-createprocessasuserw

The maximum length of this string is 32K characters.

---

Also, once there is support for msvc on windows (https://github.com/golang/go/issues/20982) it might be good idea to whitelist cl as well.