Update build.yaml (#170)

.github/workflows/build.yaml

@@ -23,7 +23,7 @@ jobs:
             os: ubuntu-latest
 
           - job_name: mac
-            os: macOS-latest
+            os: macOS-11
 
           - job_name: windows_amd64
             os: windows-latest
@@ -55,7 +55,7 @@ jobs:
         run: |
           brew update
           brew install --cask osxfuse
-        if: matrix.os == 'macOS-latest'
+        if: matrix.os == 'macOS-11'
 
       - name: Install Libraries on Windows
         shell: powershell