Add ARCTICDB_VCPKG_PACKAGES_DIR to workflow for package management

.github/workflows/run_specific_tests_on_matrix.yml

@@ -20,6 +20,7 @@ jobs:
       VCPKG_MAN_NUGET_USER: ${{secrets.VCPKG_MAN_NUGET_USER}} # For forks to download pre-compiled dependencies from the Man repo
       VCPKG_MAN_NUGET_TOKEN: ${{secrets.VCPKG_MAN_NUGET_TOKEN}}
       ARCTICDB_BUILD_DIR: ${{ inputs.os == 'windows' && 'C:/cpp_build' || '/tmp/cpp_build' }}
+      ARCTICDB_VCPKG_PACKAGES_DIR: ${{ inputs.os == 'windows' && 'C:/vcpkg_packages' || '' }}
     steps:  
       - uses: actions/[email protected]
         with: