Rebuild buildcache from scratch in nightly CI runs

.github/workflows/ResInsightMac.yml

@@ -127,8 +127,9 @@ jobs:
         with:
           path: ${{ env.BUILDCACHE_DIR }}
           key: ${{ runner.os }}-${{ matrix.arch }}-appleclang-6.7.0-buildcache-v01-${{ steps.current-time.outputs.formattedTime }}
-          restore-keys: |
-            ${{ runner.os }}-${{ matrix.arch }}-appleclang-6.7.0-buildcache-v01-
+          # The nightly scheduled run starts from an empty cache and saves a
+          # freshly built one; other runs restore the latest nightly cache.
+          restore-keys: ${{ github.event_name != 'schedule' && format('{0}-{1}-appleclang-6.7.0-buildcache-v01-', runner.os, matrix.arch) || '' }}
 
       - name: Create folder for buildcache
         run: mkdir -p "${{ env.BUILDCACHE_DIR }}"

.github/workflows/ResInsightWithCache.yml

@@ -142,6 +142,9 @@ jobs:
         run: echo "timestamp ${{ steps.current-time.outputs.formattedTime }}"
 
       - name: Restore Buildcache
+        # The nightly scheduled run starts from an empty cache and saves a
+        # freshly built one; all other runs restore the latest nightly cache.
+        if: github.event_name != 'schedule'
         id: cache-buildcache
         uses: actions/cache/restore@v6
         with: