As part of decommissioning mips support, remove the boot loader
support. Do this in advance of other boot loader work to limit the
amount of work that will be thrown away.
Sponsored by: Netflix
Reviewed by: jrtc27
Differential Revision: https://reviews.freebsd.org/D33377
simd / no float stuff is centeralized here. Also centralise
-ffreestanding since it is specified everywhere.
This, along with a change to share/mk/bsd.cpu.mk to include -mno-avx2
in CFLAGS_NO_SIMD should fix building for newer machines (eg with
CPUTYPE=haswell) where clang was generating avx2 instructions.
Sponsored by: Netflix
