CI: Enable vcpkg cache update for fuzzers build

This was a cache race condition between the fuzzers and sanitizer
builds, where the vcpkg binary cache could have been updated before the
sanitizer builds started doing their vcpkg install, causing the source
assets to never be updated at all.

.github/workflows/lagom-template.yml

@@ -150,6 +150,9 @@ jobs:
       - name: Create Build Environment (Fuzzers)
         if: ${{ inputs.build_preset == 'Fuzzers' }}
         working-directory: ${{ github.workspace }}
+        env:
+          VCPKG_CACHE_SAS: ${{ github.ref == 'refs/heads/master' && secrets.VCPKG_CACHE_SAS || '' }}
+          VCPKG_CACHE_MODE: ${{ github.ref == 'refs/heads/master' && 'write' || '' }}
         run: |
           cmake --preset=Distribution -S Meta/Lagom -B ${{ github.workspace }}/Build/tools-build \
             -DLAGOM_TOOLS_ONLY=ON \