With this I've been able to construct a set of changes to llvm-devel to allow it to cross build a dependency-free version of clang which is most of the way to having base/llvm* ports suitable for use with a root fs containing no compiler.

ping

This seems fine to me in terms of how it effects using CROSS_TOOLCHAIN for base/*, but I can't speak to whether or not checking USES directly is the best way to check for cmake.

Doing this we might miss cases where the cmake uses is inherited from a USES (which does not exist in the ports tree - yet ? but is a valid usage)

In D29236#669332, @bapt wrote:

Doing this we might miss cases where the cmake uses is inherited from a USES (which does not exist in the ports tree - yet ? but is a valid usage)

Hmm, an alternative might be do gate this on defined(GNU_CONFIGURE) instead, but I think that also suffers from the implied definition issue since this is so early in bsd.port.mk (actual code doesn't start until after line 1000).

We could also do something gross like adding an && !defined(DONT_OVERRIDE_TOOLCHAIN_FOR_CROSS_TOOLCHAIN). At the moment, I just want something that works since the current code makes it impossible to cross build cmake ports.