docker: Fix working-directory when building images

Author: ekilmer

.github/workflows/vcpkg_docker_amd64.yml

@@ -77,6 +77,7 @@ jobs:
 
       - name: Build and Push non-caching image
         if: github.ref == 'refs/heads/master'
+        working-directory: docker
         run: |
           # Only push smaller image on default branch. This could change in the
           # future if we actually need to test the smaller image before merging