Switch to LLVM 10 imminent

I don't think there was any public announcement, but most will have
surmised it by now: The base compiler will soon switch from LLVM 8
to LLVM 10 on all CLANG_ARCHS. This also concerns the linker on
LLD_ARCHS.

This will cause a certain amount of breakage in the ports tree.
We are working on it now.

I have uploaded the failure logs from early builds at
http://build-failures.rhaalovely.net/amd64-clang/

Note that the devel/pango failure prevented GTK and Qt and thus a
huge chunk of the tree from building. More meaningful logs should
appear within 24 hours.

Principal sources of build failures:
* C++ incompatibilities, as always.
* Use of -Werror breaking on new warnings.
* Linking errors.

There are also silly problems such as configure scripts misrecognizing
LLVM 10 due to changes in the output of "cc -v" or "cc -dumpversion".

Anyway, I would like to encourage more people to join into the effort.
(And yes, I'm aware that there's no publically available snapshot
or patchset with LLVM 10...)

--
Christian "naddy" Weisgerber naddy@mips.inka.de