Add support for Ubuntu 25.04 in installer script

[muaviz]

Summary of changes:

• llvm
  • Issue: GHDL doesn't support the latest version of llvm (i.e., llvm-20.1)
  • Fix: modified the installer script to install llvm-18.1
• InstallGHDL
  • Issue: Uses usr/bin/llvm-config as the configuration file (because it assumes llvm-20.1)
    ./configure --with-llvm-config=/usr/bin/llvm-config-18
  • Fix: replace that with the correct version: /usr/bin/llvm-config-18
• Gtk Canberra
  • Issue: libcanberra-gtk-module is not available to be installed in Ubuntu-25.04
  • Fix: Only install libcanberra-gtk3-module