Speed up ios simulator build check (#63)

* Cache ios dependencies (sdl2 and ffmpeg) to not download and build them each time. This should significantly speed up build check.

* Rename github workflow job step.

Author: apodrugin

.github/workflows/sourcehold.yml

@@ -61,6 +61,15 @@ jobs:
       with:
         submodules: 'true'
 
+    - name: Cache dependencies
+      if: ${{ matrix.target-platform == 'ios-simulator' }}
+      uses: actions/cache@v2
+      env:
+        cache-name: cache-${{ matrix.target-platform }}-dependencies
+      with:
+        path: ${{ github.workspace }}/thirdparty/ios
+        key: ${{ env.cache-name }}
+      
     - name: Install dependencies
       env:
         INSTALL_DEPENDENCIES: ${{ matrix.install-dependencies }}
@@ -85,7 +94,7 @@ jobs:
       run: cmake $GITHUB_WORKSPACE -DCMAKE_BUILD_TYPE=$BUILD_TYPE $CMAKE_CONFIGURE_OPTIONS
 
     - name: Build
-      working-directory: ${{github.workspace}}/build
+      working-directory: ${{ github.workspace }}/build
       shell: bash
       env:
         CMAKE_BUILD_OPTIONS: ${{ matrix.cmake-build-options }}