CI-unixish.yml: install unversioned libc++-dev package

Author: firewave

.github/workflows/CI-unixish.yml

@@ -44,10 +44,10 @@ jobs:
           sudo apt-get install valgrind
 
     - name: Install missing software on ubuntu (clang++)
-      if: matrix.os == 'ubuntu-24.04' && matrix.compiler == 'clang++'
+      if: contains(matrix.os, 'ubuntu') && matrix.compiler == 'clang++'
       run: |
         sudo apt-get update
-        sudo apt-get install libc++-18-dev
+        sudo apt-get install libc++-dev
 
       # coreutils contains "nproc"
     - name: Install missing software on macos