Add MacOS CI test builds.

.github/workflows/test.yml

@@ -5,6 +5,7 @@ on:
   pull_request:
 
 jobs:
+
   build_linux:
     name: Build Linux
     runs-on: ubuntu-latest
@@ -25,3 +26,11 @@ jobs:
       - run: |
           choco install -y llvm
           cargo build --release
+
+  build_macos:
+    name: Build MacOS
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v2
+      - run: |
+          cargo build --release