Add automatic VERSION setting for nightly builds

- Modified build.yml to accept optional version input parameter
- Modified nightly.yml to calculate VERSION from build date in format yymmddb
- VERSION is passed as PLATFORMIO_BUILD_FLAGS to override default in wled.h
- Other workflows (wled-ci.yml, release.yml) unchanged and will use default VERSION

Co-authored-by: softhack007 <91616163+softhack007@users.noreply.github.com>

.github/workflows/build.yml

@@ -3,6 +3,11 @@ name: PlatformIO CI
 # Only included into other workflows
 on:
   workflow_call:
+    inputs:
+      version:
+        description: 'Build VERSION in format yymmddb (optional, for nightly builds)'
+        required: false
+        type: string
 
 jobs:
 
@@ -62,6 +67,7 @@ jobs:
     - name: Build firmware
       env:
         WLED_RELEASE: True
+        PLATFORMIO_BUILD_FLAGS: ${{ inputs.version && format('-D VERSION={0}', inputs.version) || '' }}
       run: pio run -e ${{ matrix.environment }}
     - name: Rename Bin
       run: mv -v .pio/build/${{ matrix.environment }}/firmware.bin firmware-${{ matrix.environment }}.bin