scx_utils::BpfBuilder: properly detect clang version in Ubuntu

[arighi]

Apply the same logic of commit 00cd15a ("build: properly detect clang version in Ubuntu") in scx_utils as well.

This allows to build scx_utils properly in Ubuntu.

[htejun]

@arighi Once things look okay for ubuntu builds, please let me know. I'll cut another release so that the published scx_utils works for ubuntu out of the box.

[arighi]

@arighi Once things look okay for ubuntu builds, please let me know. I'll cut another release so that the published scx_utils works for ubuntu out of the box.

@htejun With this additional fix applied I was able to build everything in scx on Ubuntu 24.04 (and I can use the test schedulers with my own sched-ext enabled Ubuntu kernel - that I'm planning to publish soon in a ppa).

I haven't packaged scx yet, so it still requires to manually apt install a bunch of dependent packages and build everything from source, but I'm planning to create a proper deb also for the scx stuff, one step at a time. :)