Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

EFI secure boot VECTX related changes

When VECTX is enabled as a kernel option and non-EFI loaders are
built, many reads will fail due to the mis-match of whether
LOADER_VERIEXEC_VECTX or not in readin.h. Source that includes
bootstrap.h must ensure the kernel option agrees with the compile
time CFLAGS in the various make related files.

Submitted by: bret_ketchum@dell.com (original revision)
Reviewed by: sjg, bdrewery, dab, bret_ketchum@dell.com
MFC after: 1 week
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D29993

Centralize several variables.

MK_CTF, MK_SSP, MK_PROFILE, NO_PIC, and INTERNALLIB are always the
same, so set them in defs.mk. MAN= is common, so set it here too.
This removes a lot of boring repetition from the Makefiles that added
almost no value.

Move some more common stuff up to Makefile.inc. In particular, the no
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

Move sys/boot to stand. Fix all references to new location

Sponsored by: Netflix