cmd/go: stamp build settings for binaries in cmd

Also update cmd/dist to avoid setting gcflags and ldflags explicitly
when the set of flags to be set is empty (a verbose way of specifying
the default behavior).

Stamping was disabled for the Go standard library in CL 356014 due to
the cmd/dist flags causing cmd/go to (correctly) report the resulting
binaries as stale.

With cmd/dist fixed, we can also remove the special case in cmd/go,
which will allow tests of binaries in 'cmd' to read the build info
embedded in the test binary. That build info may be useful to
determine (say) whether runtime.GOROOT ought to work without GOROOT
set in the environment.

For #51483
Updates #37475

Change-Id: I64d04f5990190094eb6c0522db829d3bdfa50ef3
Reviewed-on: https://go-review.googlesource.com/c/go/+/391809
Trust: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/dist/build.go

@@ -1502,8 +1502,19 @@ func goInstall(goBinary string, args ...string) {
 	goCmd(goBinary, "install", args...)
 }
 
+func appendCompilerFlags(args []string) []string {
+	if gogcflags != "" {
+		args = append(args, "-gcflags=all="+gogcflags)
+	}
+	if goldflags != "" {
+		args = append(args, "-ldflags=all="+goldflags)
+	}
+	return args
+}
+
 func goCmd(goBinary string, cmd string, args ...string) {
-	goCmd := []string{goBinary, cmd, "-gcflags=all=" + gogcflags, "-ldflags=all=" + goldflags}
+	goCmd := []string{goBinary, cmd}
+	goCmd = appendCompilerFlags(goCmd)
 	if vflag > 0 {
 		goCmd = append(goCmd, "-v")
 	}
@@ -1517,12 +1528,11 @@ func goCmd(goBinary string, cmd string, args ...string) {
 }
 
 func checkNotStale(goBinary string, targets ...string) {
-	out := run(workdir, CheckExit,
-		append([]string{
-			goBinary,
-			"list", "-gcflags=all=" + gogcflags, "-ldflags=all=" + goldflags,
-			"-f={{if .Stale}}\tSTALE {{.ImportPath}}: {{.StaleReason}}{{end}}",
-		}, targets...)...)
+	goCmd := []string{goBinary, "list"}
+	goCmd = appendCompilerFlags(goCmd)
+	goCmd = append(goCmd, "-f={{if .Stale}}\tSTALE {{.ImportPath}}: {{.StaleReason}}{{end}}")
+
+	out := run(workdir, CheckExit, append(goCmd, targets...)...)
 	if strings.Contains(out, "\tSTALE ") {
 		os.Setenv("GODEBUG", "gocachehash=1")
 		for _, target := range []string{"runtime/internal/sys", "cmd/dist", "cmd/link"} {

src/cmd/dist/test.go

@@ -397,7 +397,9 @@ func (t *tester) registerStdTest(pkg string) {
 				"-short=" + short(),
 				t.tags(),
 				t.timeout(timeoutSec),
-				"-gcflags=all=" + gcflags,
+			}
+			if gcflags != "" {
+				args = append(args, "-gcflags=all="+gcflags)
 			}
 			if t.race {
 				args = append(args, "-race")

src/cmd/go/internal/load/pkg.go

@@ -2233,11 +2233,6 @@ var vcsStatusCache par.Cache
 // Note that the GoVersion field is not set here to avoid encoding it twice.
 // It is stored separately in the binary, mostly for historical reasons.
 func (p *Package) setBuildInfo(includeVCS bool) {
-	// TODO: build and vcs information is not embedded for executables in GOROOT.
-	// cmd/dist uses -gcflags=all= -ldflags=all= by default, which means these
-	// executables always appear stale unless the user sets the same flags.
-	// Perhaps it's safe to omit those flags when GO_GCFLAGS and GO_LDFLAGS
-	// are not set?
 	setPkgErrorf := func(format string, args ...any) {
 		if p.Error == nil {
 			p.Error = &PackageError{Err: fmt.Errorf(format, args...)}
@@ -2313,51 +2308,49 @@ func (p *Package) setBuildInfo(includeVCS bool) {
 	// Add command-line flags relevant to the build.
 	// This is informational, not an exhaustive list.
 	// Please keep the list sorted.
-	if !p.Standard {
-		if cfg.BuildASan {
-			appendSetting("-asan", "true")
-		}
-		if BuildAsmflags.present {
-			appendSetting("-asmflags", BuildAsmflags.String())
-		}
-		appendSetting("-compiler", cfg.BuildContext.Compiler)
-		if BuildGccgoflags.present && cfg.BuildContext.Compiler == "gccgo" {
-			appendSetting("-gccgoflags", BuildGccgoflags.String())
-		}
-		if BuildGcflags.present && cfg.BuildContext.Compiler == "gc" {
-			appendSetting("-gcflags", BuildGcflags.String())
-		}
-		if BuildLdflags.present {
-			appendSetting("-ldflags", BuildLdflags.String())
-		}
-		if cfg.BuildMSan {
-			appendSetting("-msan", "true")
-		}
-		if cfg.BuildRace {
-			appendSetting("-race", "true")
-		}
-		if tags := cfg.BuildContext.BuildTags; len(tags) > 0 {
-			appendSetting("-tags", strings.Join(tags, ","))
-		}
-		cgo := "0"
-		if cfg.BuildContext.CgoEnabled {
-			cgo = "1"
-		}
-		appendSetting("CGO_ENABLED", cgo)
-		if cfg.BuildContext.CgoEnabled {
-			for _, name := range []string{"CGO_CFLAGS", "CGO_CPPFLAGS", "CGO_CXXFLAGS", "CGO_LDFLAGS"} {
-				appendSetting(name, cfg.Getenv(name))
-			}
-		}
-		appendSetting("GOARCH", cfg.BuildContext.GOARCH)
-		if cfg.RawGOEXPERIMENT != "" {
-			appendSetting("GOEXPERIMENT", cfg.RawGOEXPERIMENT)
-		}
-		appendSetting("GOOS", cfg.BuildContext.GOOS)
-		if key, val := cfg.GetArchEnv(); key != "" && val != "" {
-			appendSetting(key, val)
+	if cfg.BuildASan {
+		appendSetting("-asan", "true")
+	}
+	if BuildAsmflags.present {
+		appendSetting("-asmflags", BuildAsmflags.String())
+	}
+	appendSetting("-compiler", cfg.BuildContext.Compiler)
+	if gccgoflags := BuildGccgoflags.String(); gccgoflags != "" && cfg.BuildContext.Compiler == "gccgo" {
+		appendSetting("-gccgoflags", gccgoflags)
+	}
+	if gcflags := BuildGcflags.String(); gcflags != "" && cfg.BuildContext.Compiler == "gc" {
+		appendSetting("-gcflags", gcflags)
+	}
+	if ldflags := BuildLdflags.String(); ldflags != "" {
+		appendSetting("-ldflags", ldflags)
+	}
+	if cfg.BuildMSan {
+		appendSetting("-msan", "true")
+	}
+	if cfg.BuildRace {
+		appendSetting("-race", "true")
+	}
+	if tags := cfg.BuildContext.BuildTags; len(tags) > 0 {
+		appendSetting("-tags", strings.Join(tags, ","))
+	}
+	cgo := "0"
+	if cfg.BuildContext.CgoEnabled {
+		cgo = "1"
+	}
+	appendSetting("CGO_ENABLED", cgo)
+	if cfg.BuildContext.CgoEnabled {
+		for _, name := range []string{"CGO_CFLAGS", "CGO_CPPFLAGS", "CGO_CXXFLAGS", "CGO_LDFLAGS"} {
+			appendSetting(name, cfg.Getenv(name))
 		}
 	}
+	appendSetting("GOARCH", cfg.BuildContext.GOARCH)
+	if cfg.RawGOEXPERIMENT != "" {
+		appendSetting("GOEXPERIMENT", cfg.RawGOEXPERIMENT)
+	}
+	appendSetting("GOOS", cfg.BuildContext.GOOS)
+	if key, val := cfg.GetArchEnv(); key != "" && val != "" {
+		appendSetting(key, val)
+	}
 
 	// Add VCS status if all conditions are true:
 	//