Update dirdeps.mk et al

bmake-20240309 includes updates to dirdeps and meta mode makefiles

Update meta mode makefiles

meta2deps - add checks to detect truncated/corrupted filemon data
(only known to happen on Linux hosts), to ensure we do not auto
update dependencies based on incomplete data.

meta.stage.mk adds STAGE_SHLIB_LINKS_FILTER and STAGE_LINK_AS_*

We also allow for hosts where egrep is deprecated for grep -E

Reviewed by: stevek

Update dirdeps.mk et al to latest

Move some local tweaks to local.*.mk

Reviewed by: bdrewery
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D27300

retire the LLVM_LIBUNWIND option

LLVM's libunwind is used on all FreeBSD-supported CPU architectures and
is a required component.

Reviewed by: brooks (earlier)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D23123

retire BSD_CRTBEGIN option

BSD crt is currently used on all architectures (other than sparc64).
Remove the option and use BSD crt everywhere as part of the GCC 4.2.1
retirement plan.

https://lists.freebsd.org/pipermail/freebsd-arch/2020-January/019823.html

PR: 239851
Reviewed by: andrew, brooks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D23122

Update meta* from bmake-20161212

Fix meta2deps.sh tracking of dependencies inside .CURDIR.

An example of this is in share/i18n/csmapper.

Reviewed by: sjg
Sponsored by: EMC / Isilon Storage Division

Bring meta2deps.sh closer to par with meta2deps.py

Sync FreeBSD's bmake branch with Juniper's internal bmake branch.

Requested by: Simon Gerraty <sjg@juniper.net>