cmd/go: with -x, don't report removing a non-existent objdir

Fixes #24389
Fixes #24396

Change-Id: I37399528700e2a39d9523d7c41bdc929618eb095
Reviewed-on: https://go-review.googlesource.com/102619Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/go/go_test.go

@@ -5960,3 +5960,19 @@ func TestFilepathUnderCwdFormat(t *testing.T) {
 	tg.run("test", "-x", "-cover", "log")
 	tg.grepStderrNot(`\.log\.cover\.go`, "-x output should contain correctly formatted filepath under cwd")
 }
+
+// Issue 24396.
+func TestDontReportRemoveOfEmptyDir(t *testing.T) {
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.parallel()
+	tg.tempFile("src/a/a.go", `package a`)
+	tg.setenv("GOPATH", tg.path("."))
+	tg.run("install", "-x", "a")
+	tg.run("install", "-x", "a")
+	// The second install should have printed only a WORK= line,
+	// nothing else.
+	if bytes.Count(tg.stdout.Bytes(), []byte{'\n'})+bytes.Count(tg.stderr.Bytes(), []byte{'\n'}) > 1 {
+		t.Error("unnecessary output when installing installed package")
+	}
+}

src/cmd/go/internal/work/exec.go

@@ -1136,7 +1136,11 @@ func BuildInstallFunc(b *Builder, a *Action) (err error) {
 func (b *Builder) cleanup(a *Action) {
 	if !cfg.BuildWork {
 		if cfg.BuildX {
-			b.Showcmd("", "rm -r %s", a.Objdir)
+			// Don't say we are removing the directory if
+			// we never created it.
+			if _, err := os.Stat(a.Objdir); err == nil || cfg.BuildN {
+				b.Showcmd("", "rm -r %s", a.Objdir)
+			}
 		}
 		os.RemoveAll(a.Objdir)
 	}