add back opencvdir

Author: sdcb

.github/workflows/opencvsharp.yml

@@ -147,6 +147,7 @@ jobs:
           set -eux
 
           EXTRA_FLAGS=()
+          OpenCV_DIR="${{ github.workspace }}/opencv/lib/cmake/opencv4"
 
           if [[ "${{ matrix.os }}" =~ ^win ]]; then
             OpenCV_DIR="${{ github.workspace }}/opencv/${{ matrix.arch }}/vc17/staticlib"