Archlinux doesn't package tinfo, and the non-distro maintained package
(in the AUR), doesn't provide a pkgconfig, it just symlinks libncurses.
So just pick something else. glib-2.0 is used elsewhere in meson's test
suite, so that should be safe.
This adds a depdendncy wrapper for llvm-config based on the wxwidgets
dependency. IT handles libs, version, include dir, and the llvm unique
concept of components. These components are individual pieces of the
LLVM library that may or may not be available depending on the platform.