update cmd/go flags for 1.18

As of 1.18beta1. I used bash commands like:

	diff -u <(go1.17.5 help build) <(gotip help build)

While here, supply -buildinfo=false and -buildvcs=false to go build.
We already remove that information by discarding the _gomod_.go file,
but we might as well pass the flags too.
If anything, it lets the toolchain avoid the work entirely.
Note that we can't use these flags on Go 1.17 for now, though.

Add a TODO that came to mind while writing this, too.

main.go

@@ -269,6 +269,8 @@ type errJustExit int
 
 func (e errJustExit) Error() string { return fmt.Sprintf("exit: %d", e) }
 
+var goVersionSemver string
+
 func goVersionOK() bool {
 	const (
 		minGoVersionSemver = "v1.17.0"
@@ -285,8 +287,8 @@ func goVersionOK() bool {
 		return false
 	}
 
-	versionSemver := "v" + strings.TrimPrefix(version, "go")
+	goVersionSemver = "v" + strings.TrimPrefix(version, "go")
-	if semver.Compare(versionSemver, minGoVersionSemver) < 0 {
+	if semver.Compare(goVersionSemver, minGoVersionSemver) < 0 {
 		fmt.Fprintf(os.Stderr, "Go version %q is too old; please upgrade to Go %s\n", version, suggestedGoVersion)
 		return false
 	}
@@ -487,8 +489,15 @@ This command wraps "go %s". Below is its help:
 	goArgs := []string{
 		command,
 		"-trimpath",
-		toolexecFlag.String(),
 	}
+	if semver.Compare(goVersionSemver, "v1.18.0") >= 0 {
+		// TODO: remove the conditional once we drop support for 1.17
+		goArgs = append(goArgs,
+			"-buildinfo=false",
+			"-buildvcs=false",
+		)
+	}
+	goArgs = append(goArgs, toolexecFlag.String())
 	if flagDebugDir != "" {
 		// In case the user deletes the debug directory,
 		// and a previous build is cached,
@@ -883,7 +892,7 @@ var cannotObfuscate = map[string]bool{
 	"crypto/x509/internal/macos": true,
 }
 
-// Obtained from "go list -deps runtime" on Go master (1.18) as of Nov 2021.
+// Obtained from "go list -deps runtime" on Go 1.18beta1.
 // Note that the same command on Go 1.17 results in a subset of this list.
 var runtimeAndDeps = map[string]bool{
 	"internal/goarch":         true,
@@ -1797,7 +1806,7 @@ func alterTrimpath(flags []string) []string {
 	return flagSetValue(flags, "-trimpath", sharedTempDir+"=>;"+trimpath)
 }
 
-// forwardBuildFlags is obtained from 'go help build' as of Go 1.17.
+// forwardBuildFlags is obtained from 'go help build' as of Go 1.18beta1.
 var forwardBuildFlags = map[string]bool{
 	// These shouldn't be used in nested cmd/go calls.
 	"-a": false,
@@ -1806,12 +1815,15 @@ var forwardBuildFlags = map[string]bool{
 	"-v": false,
 
 	// These are always set by garble.
-	"-trimpath": false,
+	"-trimpath":  false,
-	"-toolexec": false,
+	"-toolexec":  false,
+	"-buildinfo": false,
+	"-buildvcs":  false,
 
 	"-p":             true,
 	"-race":          true,
 	"-msan":          true,
+	"-asan":          true,
 	"-work":          true,
 	"-asmflags":      true,
 	"-buildmode":     true,
@@ -1826,10 +1838,11 @@ var forwardBuildFlags = map[string]bool{
 	"-modfile":       true,
 	"-pkgdir":        true,
 	"-tags":          true,
+	"-workfile":      true,
 	"-overlay":       true,
 }
 
-// booleanFlags is obtained from 'go help build' and 'go help testflag' as of Go 1.17.
+// booleanFlags is obtained from 'go help build' and 'go help testflag' as of Go 1.18beta1.
 var booleanFlags = map[string]bool{
 	// Shared build flags.
 	"-a":          true,
@@ -1839,9 +1852,12 @@ var booleanFlags = map[string]bool{
 	"-x":          true,
 	"-race":       true,
 	"-msan":       true,
+	"-asan":       true,
 	"-linkshared": true,
 	"-modcacherw": true,
 	"-trimpath":   true,
+	"-buildinfo":  true,
+	"-buildvcs":   true,
 
 	// Test flags (TODO: support its special -args flag)
 	"-c":        true,

shared.go

@@ -159,6 +159,9 @@ func (p *listedPackage) obfuscatedImportPath() string {
 // and all of its dependencies
 func appendListedPackages(patterns ...string) error {
 	startTime := time.Now()
+	// TODO: perhaps include all top-level build flags set by garble,
+	// including -buildinfo=false and -buildvcs=false.
+	// They shouldn't affect "go list" here, but might as well be consistent.
 	args := []string{"list", "-json", "-deps", "-export", "-trimpath"}
 	args = append(args, cache.ForwardBuildFlags...)
 	args = append(args, patterns...)