Use SCons cache on CI to improve build times

.github/workflows/build-addon-on-push.yml

@@ -3,6 +3,11 @@ name: Build on push
 
 on: [push, pull_request]
 
+env:
+  # Only used for the cache key. Increment version to force clean build.
+  GODOT_BASE_BRANCH: master
+  SCONS_CACHE: ${{ github.workspace }}/.scons-cache/
+
 jobs:
   build:
     name: Building for ${{ matrix.name }} (${{ matrix.os }})
@@ -17,42 +22,49 @@ jobs:
             flags: arch=x86_64
             artifact_name: build-files-linux-x86_64
             artifact_path: aar/demo/addons/godotopenxrvendors/.bin/linux/*/*/*.so
+            cache-name: linux-x86_64
           # Not sure how to cross compile these
           # - name: Linux (arm64)
           #   os: ubuntu-20.04
           #   platform: linux
           #   flags: arch=arm64
-          #  artifact_name: build-files-linux-arm64
+          #   artifact_name: build-files-linux-arm64
           #   artifact_path: aar/demo/addons/godotopenxrvendors/.bin/linux/*/*/*.so
+          #   cache-name: linux-arm64
           # - name: Linux (rv64)
           #  os: ubuntu-20.04
           #  platform: linux
           #  flags: arch=rv64
           #  artifact_name: build-files-linux-rv64
           #  artifact_path: aar/demo/addons/godotopenxrvendors/.bin/linux/*/*/*.so
+          #  cache-name: linux-rv64
           - name: Windows
             os: windows-latest
             platform: windows
             artifact_name: build-files-windows
             artifact_path: aar/demo/addons/godotopenxrvendors/.bin/windows/*/*/*.dll
+            cache-name: windows-x86_64
           - name: MacOS
             os: macos-latest
             platform: macos
             flags: arch=universal
             artifact_name: build-files-macos
             artifact_path: aar/demo/addons/godotopenxrvendors/.bin/macos/*/*.framework
+            cache-name: macos-universal
           - name: Android AAR
             os: ubuntu-20.04
             platform: android
             flags: arch=arm64
             artifact_name: build-files-android-aar
             artifact_path: aar/demo/addons/godotopenxrvendors/.bin/android/*/*.aar
+            cache-name: android-aar
           - name: Android SO
             os: ubuntu-20.04
             platform: android
             flags: arch=arm64
             artifact_name: build-files-android-so
             artifact_path: aar/demo/addons/godotopenxrvendors/.bin/android/*/*/*.so
+            cache-name: android-so
 
     # Note, to satisfy the asset library we need to make sure our zip files have a root folder
     # this is why we checkout into aar and build into asset
@@ -62,6 +74,11 @@ jobs:
         with:
           path: aar
           submodules: recursive
+      - name: Setup Godot build cache
+        uses: ./aar/thirdparty/godot-cpp/.github/actions/godot-cache
+        with:
+          cache-name: ${{ matrix.cache-name }}
+        continue-on-error: true
       - name: Set up Python (for SCons)
         uses: actions/setup-python@v4
         with: