MFC r282057,r282092,r282106:

r282057:

Build/install libc, librt, libthr, and msun NetBSD test suites on all
architectures

r282092 (by andrew):

Correct the spelling of MACHINE_CPUARCH, MACHINE_CPU is not set on arm64.

r282106:

Remove per-architecture checks for enabling HAVE_FENV_H

The conditional came from NetBSD, where only select architectures have this
header/support

All architectures on FreeBSD have the necessary support though, so the
conditional's completely unnecessary

make tinderbox done on all architectures (including arm64, where the issue
occurred before) this time