Fix GitHub Actions go-gl module issue

- Clone go-gl repo locally during build
- Add replace directive pointing to ./go-gl-temp
- Run go mod tidy to update go.sum
- Fixes 'missing go.sum entry' error for all platform builds

Author: Jayden Thorup

.github/workflows/build.yml

@@ -53,6 +53,13 @@ jobs:
         sudo apt-get update
         sudo apt-get install -y gcc libgl1-mesa-dev xorg-dev
 
+    - name: Setup go-gl workaround
+      run: |
+        git clone https://github.com/go-gl/gl.git go-gl-temp
+        echo "" >> go.mod
+        echo "replace github.com/go-gl/gl => ./go-gl-temp" >> go.mod
+        go mod tidy
+
     - name: Build (Windows)
       if: matrix.os == 'windows-latest'
       env: