[NFC] Update GH action for Windows for testing

While I'm trying to fix building on Windows, I need this action to run
on every push.

.github/workflows/x86-windows-llvm-from-sources.yml

@@ -1,6 +1,7 @@
 name: x86-Windows-llvm-from-sources
 
 on: 
+  push:
   schedule:
     - cron:  '0 0 * * *'