build failures for Clang

Hi,

since several weeks the Clang builds are failing.

https://releng.netbsd.org/cgi-bin/builds.cgi

I already fixed a few of the previous build failures, but I am clueless
with this one, which makes 6 of the 8 builds fail:

undefined reference to `std::__1::codecvt<char, char, int>::id'

Could someone familiar with the C++ standard library perhaps have a look
at this?

evbarm-aarch64 fails with:

/usr/include/arm/lock.h:212:20: error:
     invalid instruction, did you mean:
     stcl, stl, stlb, stlh, str, strb, strd, strh, strt?
     __asm __volatile("stlr\t%0, [%1]"

evbarm-earmv6hf fails even more spectacularly by triggering an internal
compiler error in Clang:

xsrc/external/mit/xf86-video-nouveau/dist/src/nv10_exa.c

Any idea how to fix these remaining issues?

Roland