Add freebsd build (#172)

.github/workflows/build.yml

@@ -35,6 +35,21 @@ jobs:
     - name: Test
       run:  ctest -VV
 
+  freebsd:
+    runs-on: macos-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Build and Test
+      uses: vmactions/freebsd-vm@v0.1.2
+      with:
+        usesh: true
+        prepare: pkg install -y cmake tree lang/gcc
+        run: |
+          cmake .
+          cmake --build .
+          tree -sha .
+          ctest -VV
+
   windows-msvc:
     runs-on: "windows-latest"
     steps: