Don't overwrite build info unless Glean will get initialized.

Previously a second invocation of Glean.initialize would override the stored build
info, even if no other work was done due to Glean already being
initialized.

glean-core/android/src/main/java/mozilla/telemetry/glean/Glean.kt

@@ -139,8 +139,6 @@ open class GleanInternalAPI internal constructor () {
         configuration: Configuration = Configuration(),
         buildInfo: BuildInfo
     ) {
-        this.buildInfo = buildInfo
-
         // Glean initialization must be called on the main thread, or lifecycle
         // registration may fail. This is also enforced at build time by the
         // @MainThread decorator, but this run time check is also performed to
@@ -159,6 +157,7 @@ open class GleanInternalAPI internal constructor () {
             return
         }
 
+        this.buildInfo = buildInfo
         this.applicationContext = applicationContext
 
         this.configuration = configuration