Reapply "Set build version during nightly build" - doesn't work as source

This reverts commit 471bd83eb2.

.github/workflows/nightly.yml

@@ -8,7 +8,15 @@ on:
   workflow_dispatch:
 
 jobs:
+  prep:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set Version
+        run: |
+          VERSION=`date +%y%m%d0`
+          sed -i -r -e "s/#define VERSION .+/#define VERSION $VERSION/" wled00/wled.h
   wled_build:
+    needs: prep
     uses: ./.github/workflows/build.yml
   nightly:
     name: Deploy nightly