Build Tests: Fix Contiki build on macOS

Add libtool to the brew setup.

.github/workflows/main.yml

@@ -126,7 +126,7 @@ jobs:
     - uses: actions/checkout@v4
     - name: install macOS software
       run: |
-        brew install make automake
+        brew install make automake libtool
     - name: setup
       run: |
         ./autogen.sh