cmd/go: go test -race -i runtime/race must not install race-enabled cmd/cgo

Fix now uses same test as 'go build'.

Fixes #10500.

Change-Id: I2fcf2d95430643370aa29165d89a188988dee446
Reviewed-on: https://go-review.googlesource.com/12174Reviewed-by: Rob Pike <r@golang.org>

src/cmd/go/go_test.go

@@ -2077,3 +2077,20 @@ func TestGoInstallPkgdir(t *testing.T) {
 	_, err = os.Stat(filepath.Join(pkg, "runtime.a"))
 	tg.must(err)
 }
+
+func TestGoTestRaceInstallCgo(t *testing.T) {
+	// golang.org/issue/10500.
+	// This used to install a race-enabled cgo.
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.run("tool", "-n", "cgo")
+	cgo := strings.TrimSpace(tg.stdout.String())
+	old, err := os.Stat(cgo)
+	tg.must(err)
+	tg.run("test", "-race", "-i", "runtime/race")
+	new, err := os.Stat(cgo)
+	tg.must(err)
+	if new.ModTime() != old.ModTime() {
+		t.Fatalf("go test -i runtime/race reinstalled cmd/cgo")
+	}
+}

src/cmd/go/test.go

@@ -386,7 +386,7 @@ func runTest(cmd *Command, args []string) {
 		if deps["C"] {
 			delete(deps, "C")
 			deps["runtime/cgo"] = true
-			if buildContext.GOOS == runtime.GOOS && buildContext.GOARCH == runtime.GOARCH {
+			if goos == runtime.GOOS && goarch == runtime.GOARCH && !buildRace {
 				deps["cmd/cgo"] = true
 			}
 		}