Enable macOS and Windows CI builds

These will most likely break

.github/workflows/ci.yml

@@ -1,25 +1,37 @@
 name: CI
 on: [push]
 jobs:
-    linux:
-        runs-on: ubuntu-latest
-        env:
-            CC: gcc-9
-            CXX: g++-9
-        steps:
-        - uses: actions/checkout@v2
-        - name: Download LunarG key
-          run: wget -qO - https://packages.lunarg.com/lunarg-signing-key-pub.asc | sudo apt-key add -
-        - name: Add LunarG Vulkan repository
-          run: sudo wget -qO /etc/apt/sources.list.d/lunarg-vulkan-bionic.list https://packages.lunarg.com/vulkan/lunarg-vulkan-bionic.list
-        - name: Update package list
-          run: sudo apt update
-        - name: Install Vulkan SDK
-          run: sudo apt install -f vulkan-sdk libsdl2-dev
-        - name: Configure
-          run: cmake -S. -Bbuild -DCMAKE_BUILD_TYPE=Release
-        - name: Build
-          run: cmake --build build --target all -v
+    job:
+      name: ${{ matrix.os }}-${{ github.workflow }}
+      runs-on: ${{ matrix.os }}
+      strategy:
+        fail-fast: false
+        matrix:
+          os: [ ubuntu-latest, macos-latest, windows-latest ]
+          include:
+            - os: windows-latest
+              triplet: x64-windows
+            - os: ubuntu-latest
+              triplet: x64-linux
+            - os: macos-latest
+              triplet: x64-osx
+      steps:
+      - uses: actions/checkout@v2
+      - name: Download LunarG key
+        run: wget -qO - https://packages.lunarg.com/lunarg-signing-key-pub.asc | sudo apt-key add -
+      - name: Add LunarG Vulkan repository
+        if: matrix.os == 'ubuntu-latest'
+        run: sudo wget -qO /etc/apt/sources.list.d/lunarg-vulkan-bionic.list https://packages.lunarg.com/vulkan/lunarg-vulkan-bionic.list
+      - name: Update package list
+        if: matrix.os == 'ubuntu-latest'
+        run: sudo apt update
+      - name: Install Vulkan SDK
+        if: matrix.os == 'ubuntu-latest'
+        run: sudo apt install -f vulkan-sdk libsdl2-dev
+      - name: Configure
+        run: cmake -S. -Bbuild -DCMAKE_BUILD_TYPE=Release
+      - name: Build
+        run: cmake --build build --target all -v
 
     windows:
         runs-on: windows-latest