Set workspaces in Swatinem/rust-cache to rust-src-dir if cache-workspaces is not set

Author: Kubaryt

action.yml

@@ -229,7 +229,7 @@ runs:
       if: inputs.cache == 'true'
       uses: Swatinem/rust-cache@v2
       with:
-        workspaces: ${{inputs.cache-workspaces}}
+        workspaces: ${{ inputs.cache-workspaces || inputs.rust-src-dir }}
         cache-directories: ${{inputs.cache-directories}}
         cache-on-failure: ${{inputs.cache-on-failure}}
         cache-bin: ${{inputs.cache-bin}}