action.yml: properly remove temporary files after downloading

Remove `.tgz` and `.msi` files after they have been downloaded. This was
the behaviour of the action previous to `v3.2.0`, but our logic for
caching removed the deletion of these files.

Can look at downloading these to temp folders to avoid the more complex
logic here as a follow up, but this should unblock / fix the immediate
regression.

Also, on Windows, write `tailscale.log` to the temp dir.

Also, on MacOS, delete the `tailscale` directory that was used to build the `tailscale(d)` commands.

Updates: #170

Co-authored-by: Mario Minardi <mario@tailscale.com>
Signed-off-by: Percy Wegmann <percy@tailscale.com>

.github/workflows/tailscale.yml

@@ -14,6 +14,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
+        cache: ['false', 'true']
     runs-on: ${{ matrix.os }}
     steps:
       - name: Check out code
@@ -25,8 +26,19 @@ jobs:
           oauth-client-id: ${{ secrets.TS_OAUTH_CLIENT_ID }}
           oauth-secret: ${{ secrets.TS_OAUTH_SECRET }}
           tags: tag:ci
+          use-cache: ${{ matrix.cache }}
 
       - name: check for tailscale connection
         shell: bash
         run:
           tailscale status -json | jq -r .BackendState | grep -q Running
+
+      - name: ensure no dirty files from Tailscale Action remain
+        shell: bash
+        run: |
+          extra_files=$(git ls-files . --exclude-standard --others)
+          if [ ! -z "$extra_files" ]; then
+            echo "::error::Unexpected extra files: $extra_files"
+            exit 1
+          fi
+