I've noticed the discussion on Boost 2 where build2 was mentioned as
one of the potential build systems. So I wanted to say that we would
be happy to help on our side with any questions, missing features
(like exporting targets in a CMake-compatible manner, as mentioned
by Niall), etc.
Also a couple of additional points about build2 that I think could
be relevant to Boost 2 (or 1):
1. It is currently the only build system that I am aware of that has
support for C++ modules (currently TS but we are tracking the
standardization/implementation progress closely; see  for
details). Now that modules are likely to be in C++20 I think
this should be at least a consideration for Boost 2.
2. We have a public CI service for open source project that I think
could be quite useful to Boost. It might not currently be as extensive
as Boost's (see  for the currently offered build configurations)
but we are continuously expanding it plus Boost can run its own build
machines with additional configurations.
3. build2 comes with a package manager and Boost could take advantage
of that by either publishing to cppget.org or running its own package
repository (or both).
I am happy to answer any questions here (if appropriate, of course), on
the build2 mailing list, or on the #build2 slack channel.