openbsd: skip tests using Dir.realpath

[semarie]

The Dir.realpath() implementation is based on getFdPath(), which doesn't exist on OpenBSD (or some others OS like FreeBSD). Disable the tests using it for now.

I am thinking about some ways to provide alternative implementation, for example:

• add the know pathname used to open the descriptor in zig structure and resolv it on demand with realpath(); but not all descriptors are opened with a name: on exec you could have an already open descriptor, or you could receive descriptor from UNIX socket
• iterate on descriptor to retreive the name from filesystem (with openat(fd, "..") and searching for the right inode with fstat()) ; but it could be permission issue to read directory content
• call chdir() on the descriptor and read the path with getcwd() ; but it is bad when threads are involved (it changes a global parameter)

I will see that later.

[kubkon]

That's really interesting! I thought that only FreeBSD lacked facilities to implement getFdPath() but evidently it is not so. So OpenBSD doesn't have a mechanism similar to macOS's custom fcntl commands, or Linux's /proc hack?

BTW, while we're here, I'd like to propose that we start looking out for an OpenBSD CI somewhere. As far as I can see we don't currently test this target, and I'd hate to introduce a regression just because we didn't have the testing harness in place. This would nullify a lot of your great hard work on this @semarie.

[semarie]

OpenBSD doesn't have such mecanism for getting the path of the current process, and even more so for a random file descriptor 😃

Regarding CI, for me it is too early. Regarding OpenBSD support:

• llvm11 source tree needs patches to support OpenBSD
• libc++, libc++abi and libunwind needs patches to support OpenBSD (the ones from zig doesn't compile - I patched zig to use the host libraries to workaround)