* Support building on OpenBSD, x86-64
* Clean up OpenBSD Makefile
* Add OpenBSD to cmake build
* Use clang as CC for OpenBSD
Co-authored-by: Alex Segura <alex@lispm.dev>
We currently build for ISO C90 with GNU extensions. The GNU
extensions include both library and language features.
Compiling without GNU extensions results in a number of compilation
failures due to use of those library features.
With this, we'll build for ISO C99 with the GNU extensions and
can evaluate what's going on with those library features in the
future.
This doesn't remove or replace the existing build system, but
provides an alternative. It allows for faster builds with proper
incremental builds, as well as using tools such as `clang-tidy`,
which work better when they have a compiler commands 'database'.
