version: use vcs.revision for version.Build in dlv version command

The build ID wasn't properly set/determined when calling `dlv version`
command. It kept showing the very old hash (not git hash though) of
`7e679e5860c17d90514f9c440e055355de831ce2`. This is because we are
searching for the git hash in build info via `gitrevision` key's value
which doesn't exist in the Go build info, and since we simply return
without error if nothing is found, it kept using the old hash of
`7e679e5860c17d90514f9c440e055355de831ce2` (note, I still couldn't
determine where this comes from, so I've maintained backwards
compatibility detailed below).

Go build info's git revision hash key is `vcs.revision`. So, I added
logic to search for that and attach its value to the version.Build
field. If nothing is found and haven't return its value, then we try
searching for `gitrevision` which maintains backwards compatibility.

Fixes #3986

Author: codeaucafe

pkg/version/fixbuild.go

@@ -9,14 +9,27 @@ func init() {
 }
 
 func buildInfoFixBuild(v *Version) {
+	if v.Build != "$Id$" {
+		return
+	}
+
 	info, ok := debug.ReadBuildInfo()
 	if !ok {
 		return
 	}
-	for i := range info.Settings {
-		if info.Settings[i].Key == "gitrevision" {
-			v.Build = info.Settings[i].Value
-			break
+
+	for _, setting := range info.Settings {
+		if setting.Key == "vcs.revision" {
+			v.Build = setting.Value
+			return
+		}
+	}
+
+	// If we didn't find vcs.revision, try the old key for backward compatibility
+	for _, setting := range info.Settings {
+		if setting.Key == "gitrevision" {
+			v.Build = setting.Value
+			return
 		}
 	}
 }