ci: Always use the latest Android build tools

Taken from r0adkll/sign-android-release#84

.github/workflows/android.yml

@@ -67,6 +67,13 @@ jobs:
       if: success()
       run: ./gradlew :app:assembleRelease
 
+    - name: Setup build tool version variable
+      shell: bash
+      run: |
+        BUILD_TOOL_VERSION=$(ls /usr/local/lib/android/sdk/build-tools/ | tail -n 1)
+        echo "BUILD_TOOL_VERSION=$BUILD_TOOL_VERSION" >> $GITHUB_ENV
+        echo Last build tool version is: $BUILD_TOOL_VERSION
+
     - name: Sign release APK
       if: success()
       uses: r0adkll/sign-android-release@v1
@@ -77,6 +84,8 @@ jobs:
         alias: ${{ secrets.KEY_ALIAS }}
         keyStorePassword: ${{ secrets.KEY_STORE_PASSWORD }}
         keyPassword: ${{ secrets.KEY_PASSWORD }}
+      env:
+        BUILD_TOOLS_VERSION: ${{ env.BUILD_TOOL_VERSION }}
 
     - name: Build release AAB
       if: success()
@@ -92,6 +101,8 @@ jobs:
         alias: ${{ secrets.KEY_ALIAS }}
         keyStorePassword: ${{ secrets.KEY_STORE_PASSWORD }}
         keyPassword: ${{ secrets.KEY_PASSWORD }}
+      env:
+        BUILD_TOOLS_VERSION: ${{ env.BUILD_TOOL_VERSION }}
 
     - name: Create CHANGELOG
       id: changelog