github: Evict old entries from ccache

We don't want to build old versions using these caches, so we don't
need old entries (if header files change, there could be lots of
differences that increase the cache size unnecessarily).

.github/workflows/android.yml

@@ -13,6 +13,7 @@ env:
   CCACHE_BASEDIR: ${{ github.workspace }}
   CCACHE_COMPRESS: true
   CCACHE_MAXSIZE: 150M
+  EVICT_CCACHE_AGE: 1200s
   CC: gcc
   OS_NAME: linux
 
@@ -68,6 +69,10 @@ jobs:
         with:
           name: Lint Results
           path: src/frontends/android/app/build/reports/lint-results*.xml
+      - if: github.event_name == 'push'
+        run: |
+          ccache --evict-older-than ${{ env.EVICT_CCACHE_AGE }}
+          ccache -sv
       # delete old cache entry as we currently can't update it any other way
       - env:
           GH_TOKEN: ${{ github.token }}