We've found that there are cases where it's useful to be able to include
the same target in multiple distributions (e.g. if you want a
distribution that's a superset of another distribution, for convenience
purposes), and that there are cases where the distribution of a target
and its umbrella can legitimately differ (e.g. the LTO library would
commonly be distributed alongside your tools, but it also falls under
the llvm-libraries umbrella, which would commonly be distributed
separately). Relax the restrictions while providing an option to restore
them (which is mostly useful to ensure you aren't accidentally placing
targets in the wrong distributions).
There could be further refinements here (e.g. excluding a target from an
umbrella if it's explicitly included in some other distribution, or
having variables to control which targets are allowed to be duplicated
or placed in a separate distribution than their umbrellas), but we can
punt on those until there's an actual need.
LLVM's build system contains support for configuring a distribution, but
it can often be useful to be able to configure multiple distributions
(e.g. if you want separate distributions for the tools and the
libraries). Add this support to the build system, along with
documentation and usage examples.
Reviewed By: phosek
Differential Revision: https://reviews.llvm.org/D89177
This extracts the LLVM distribution target handling into a support module.
Extraction will enable us to restructure the builds to support multiple
distribution configurations (e.g. developer and user) to permit us to build the
development package and the user package at once.
llvm-svn: 363440
Shoaib Meenai