CI: Install egl headers in msys setup

Author: eliemichel

.github/workflows/cmake.yml

@@ -62,7 +62,7 @@ jobs:
       uses: msys2/setup-msys2@v2
       with:
         msystem: ${{ matrix.msystem }}
-        pacboy: cmake:p
+        pacboy: cmake:p egl-headers:p
 
     - name: Configure CMake
       run: >