appdata: When looking for appdata, find canonical name first

bijben had both a metainfo and an appdata, which caused EEXIST when
renaming the file.

src/builder-manifest.c

@@ -2131,13 +2131,16 @@ static GFile *
 builder_manifest_find_appdata_file (BuilderManifest *self,
 				    GFile *app_root)
 {
+  /* We order these so that share/appdata/*.appdata.xml if found
+     first, as this is the target name, and apps may have both, which will
+     cause issues with the rename. */
   const char *extensions[] = {
-    ".metainfo.xml",
     ".appdata.xml",
+    ".metainfo.xml",
   };
   const char *dirs[] = {
-    "share/metainfo",
     "share/appdata",
+    "share/metainfo",
   };
   g_autoptr(GFile) source = NULL;