Raise Git's http.postBuffer to something high for macOS actions

.github/workflows/macos-cmake.yaml

@@ -8,6 +8,8 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
+    - name: Set Git http.postBuffer to something high
+      run: git config --global http.postBuffer 524288000
     - name: Update brew repos
       run: brew update
     - name: Tap RfidResearchGroup/proxmark3