Update workflow now that the ubuntu-latest image is 24.04

GitHub's Ubuntu 24.04 image has fewer development packages pre-installed
than 22.04 did previously; ensure that libbz2 development files are present.

Author: jmarshall

.github/workflows/unix-build.yml

@@ -32,6 +32,8 @@ jobs:
     - name: Ubuntu-latest using gcc with sanitizers
       if: runner.os == 'Linux'
       run: |
+        sudo apt-get update
+        sudo apt-get install -y --no-install-suggests --no-install-recommends libbz2-dev
         autoreconf -i
         ./configure CC="gcc -fsanitize=address,undefined"