gh: export PATH before installing

.github/workflows/ci.yml

@@ -33,8 +33,8 @@ jobs:
           sudo apt install protobuf-compiler --yes
       - name: Install Nushell
         run: |
-          make install-nu
           echo "PATH=\"$(make print-NU_DEST):$PATH\"" >> $GITHUB_ENV
+          make install-nu
       - name: Show configuration
         run: make show
       - name: Run tests