[build2] Build error on openbsd 7.1

Tue May 17 10:05:50 UTC 2022

Dirty Dawn via users <users at build2.org> writes:

> ld: error: libbutl/libbutl/libbutl-stage-0.15.0-a.0.6ebefaae2072.so:
> undefined reference to vtable for butl::uuid_system_generator [--no-allow-shlib-undefined]

Ok, I've added OpenBSD support in the UUID generation code. I've
also looked through all the FreeBSD/NetBSD-specific code and made
corresponding changes for OpenBSD. Could you re-test the latest
staged toolchain?