cmd/*, lib/build: Set correct LongVersion (fixes #5993) (#5997)

The relay and discosrv didn't use the new lib/build package, now they
do. Conversely the lib/build package wasn't aware there might be other
users and hard coded the program name - now it's set by the build
script

lib/build/build.go

@@ -18,10 +18,11 @@ import (
 
 var (
 	// Injected by build script
+	Program = "syncthing"
 	Version = "unknown-dev"
-	Host    = "unknown" // Set by build script
-	User    = "unknown" // Set by build script
-	Stamp   = "0"       // Set by build script
+	Host    = "unknown"
+	User    = "unknown"
+	Stamp   = "0"
 
 	// Static
 	Codename = "Fermium Flea"
@@ -73,7 +74,7 @@ func setBuildData() {
 	Date = time.Unix(int64(stamp), 0)
 
 	date := Date.UTC().Format("2006-01-02 15:04:05 MST")
-	LongVersion = fmt.Sprintf(`syncthing %s "%s" (%s %s-%s) %s@%s %s`, Version, Codename, runtime.Version(), runtime.GOOS, runtime.GOARCH, User, Host, date)
+	LongVersion = fmt.Sprintf(`%s %s "%s" (%s %s-%s) %s@%s %s`, Program, Version, Codename, runtime.Version(), runtime.GOOS, runtime.GOARCH, User, Host, date)
 
 	if len(Tags) > 0 {
 		LongVersion = fmt.Sprintf("%s [%s]", LongVersion, strings.Join(Tags, ", "))