Allow to build with the PyPI package "clang" instead of "libclang". 1. It seems to be maintained. 2. In the FreeBSD base system there is no pre-built libclang.so. If you need this library you have to install llvm from ports additionally. 2. On FreeBSD there is no pre-built wheel "libclang" with a packaged libclang.so.

# Build in a non-isolated venv
#
# cmake is required as a system package: could not build it as Python package
# on the fly.
#
# gmake is to be used!
#
setuptools
setuptools-scm
build
swig
clang>=18,<19