Update main_ci.yml

Author: aers

.github/workflows/main_ci.yml

@@ -31,7 +31,10 @@ jobs:
       - uses: actions/checkout@v2
         with:
           submodules: 'true'
-
+      - name: "Set environmental variables"
+        shell: bash
+        run: |
+          echo "VCPKG_ROOT=$VCPKG_INSTALLATION_ROOT" >> $GITHUB_ENV
       - name: Setup vcpkg
         run: |
           mkdir -p ${{ env.VCPKG_DEFAULT_BINARY_CACHE }}