cmd/go: avoid hard-coding runtime dependencies in TestNewReleaseRebui…

…ldsStalePackagesInGOPATH

Fixes golang#64583.

Change-Id: Idbe50fe77f6030f2402ac436abe6710cb1183730
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest,gotip-windows-amd64-longtest
Reviewed-on: https://go-review.googlesource.com/c/go/+/547995
Reviewed-by: Russ Cox <rsc@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/go/go_test.go

@@ -881,22 +881,17 @@ func TestNewReleaseRebuildsStalePackagesInGOPATH(t *testing.T) {
 
 	// Copy the runtime packages into a temporary GOROOT
 	// so that we can change files.
-	for _, copydir := range []string{
-		"src/runtime",
-		"src/internal/abi",
-		"src/internal/bytealg",
-		"src/internal/coverage/rtcov",
-		"src/internal/cpu",
-		"src/internal/goarch",
-		"src/internal/godebugs",
-		"src/internal/goexperiment",
-		"src/internal/goos",
-		"src/internal/coverage/rtcov",
-		"src/math/bits",
-		"src/unsafe",
+	var dirs []string
+	tg.run("list", "-deps", "runtime")
+	pkgs := strings.Split(strings.TrimSpace(tg.getStdout()), "\n")
+	for _, pkg := range pkgs {
+		dirs = append(dirs, filepath.Join("src", pkg))
+	}
+	dirs = append(dirs,
 		filepath.Join("pkg/tool", goHostOS+"_"+goHostArch),
 		"pkg/include",
-	} {
+	)
+	for _, copydir := range dirs {
 		srcdir := filepath.Join(testGOROOT, copydir)
 		tg.tempDir(filepath.Join("goroot", copydir))
 		err := filepath.WalkDir(srcdir,
@@ -912,6 +907,9 @@ func TestNewReleaseRebuildsStalePackagesInGOPATH(t *testing.T) {
 					return err
 				}
 				dest := filepath.Join("goroot", copydir, srcrel)
+				if _, err := os.Stat(dest); err == nil {
+					return nil
+				}
 				data, err := os.ReadFile(path)
 				if err != nil {
 					return err