feat: use brew llvm and restablish macos-15 bottle support

[tuler]

Previous formula relied on system make and clang version.
But cartesi-machine requires C++23, and reportedly tested with clang >= 19.
macOS 15 (sequoia) command line tools only provides apple clang 17. So for that OS user must install brew llvm on his own.
This change the formula to use its own llvm dependency, forcing build to always use it, regardless the system clang.

[tuler]

The problem is that the following formulas do not provide macos15-intel Sequoia bottles, only for macos14-intel Sonoma, so a bottle is not built. But macos14 GitHub runners are deprecated and will not be available anymore in a near future.
Homebrew also is not building bottles for Sequoia, only for Sonoma, with a plan to drop intel completely soon.

boost
llvm
libomp
libslirp
lua@5.4

So we can keep macOS-15 in the matrix, forcing llvm, but we probably should drop intel.