CI: Use more cores available

There is no easy cross platform way I know about.

Author: jdupak

.github/workflows/debug.yml

@@ -86,7 +86,7 @@ jobs:
 
       - name: Build
         working-directory: ${{ github.workspace }}/build
-        run: cmake --build . -j3
+        run: cmake --build . -j4
 
       - name: Test
         working-directory: ${{ github.workspace }}/build
@@ -196,7 +196,7 @@ jobs:
 
       - name: Build
         working-directory: ${{ github.workspace }}/build
-        run: cmake --build . -j3
+        run: cmake --build . -j4
 
       - name: Deploy on Windows
         if: runner.os == 'Windows'