attempt to cache our arduino downloads

.github/workflows/build.yml

@@ -11,15 +11,28 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
+    - uses: actions/cache@v2
+        id: arduino-cache
+        with:
+            path: |
+              ${{ github.workspace }}/.arduino/data
+              ${{ github.workspace }}/.arduino/downloads
+            key: ${{ runner.os }}-arduino
 
 ## We delete the Bundle's version of Kaleidoscope, and symlink ourselves in.
 ## This makes sure we're using the current version of the library.
     - run: sudo apt-get install ccache
     - run: git clone --depth 1 --recurse-submodules=build-tools --recurse-submodules=toolchain --recurse-submodules=avr/libraries/ --jobs 16 --shallow-submodules git://github.com/keyboardio/Kaleidoscope-Bundle-Keyboardio $ARDUINO_DIRECTORIES_USER/hardware/keyboardio
     # - run: make adjust-git-timestamps
-    - run: make install-arduino-cli
-    - run: make configure-arduino-cli
-    - run: make install-arduino-core-avr
+    - name: Install arduino cli
+      if: steps.arduino-cache.outputs.cache-hit != 'true'
+      run: make install-arduino-cli
+    - name: Configure arduino cli
+      if: steps.arduino-cache.outputs.cache-hit != 'true'
+      run: make configure-arduino-cli
+    - name: Install arduino avr core
+      if: steps.arduino-cache.outputs.cache-hit != 'true'
+      run: make install-arduino-core-avr
     - run: make smoke-sketches
   run-google-tests:
     runs-on: ubuntu-latest
@@ -29,9 +42,15 @@ jobs:
     - run: sudo apt-get install ccache
     - run: git clone --depth 1 --recurse-submodules=build-tools --recurse-submodules=toolchain --recurse-submodules=avr/libraries/ --jobs 16 --shallow-submodules git://github.com/keyboardio/Kaleidoscope-Bundle-Keyboardio $ARDUINO_DIRECTORIES_USER/hardware/keyboardio
     # - run: make adjust-git-timestamps
-    - run: make install-arduino-cli
-    - run: make configure-arduino-cli
-    - run: make install-arduino-core-avr
+    - name: Install arduino cli
+      if: steps.arduino-cache.outputs.cache-hit != 'true'
+      run: make install-arduino-cli
+    - name: Configure arduino cli
+      if: steps.arduino-cache.outputs.cache-hit != 'true'
+      run: make configure-arduino-cli
+    - name: Install arduino avr core
+      if: steps.arduino-cache.outputs.cache-hit != 'true'
+      run: make install-arduino-core-avr
     - run: make prepare-virtual
     - run: make simulator-tests
   check-astyle: