Update build script

Author: davidmezzetti

.github/workflows/build.yml

@@ -28,7 +28,8 @@ jobs:
         if: matrix.os != 'ubuntu-latest'
 
       - name: Install dependencies - macOS
-        run: brew install libomp
+        run: |
+          echo "OMP_NUM_THREADS=1" >> $GITHUB_ENV
         if: matrix.os == 'macos-latest'
 
       - name: Install dependencies - Windows