CI: add libutfcpp-dev in some Linux builds to test detection

(cherry picked from commit e133286)

Author: robUx4

.github/workflows/linux.yaml

@@ -10,6 +10,10 @@ jobs:
     name: libebml for Linux
     runs-on: ubuntu-latest
     steps:
+      - name: install utf8cpp
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends libutfcpp-dev
 
       - name: Get pushed code
         uses: actions/checkout@v4