CI: Setup python for OSX

Author: d3m3vilurr

.github/workflows/build.yml

@@ -37,6 +37,7 @@ jobs:
     runs-on: macos-10.15
     steps:
     - uses: actions/checkout@v2
+    - uses: actions/setup-python@v2
     - name: Build
       run: |
         git config --global user.email "builds@travis-ci.com"