MK_FORTH: Allow removing loader.4th w/ delete-old

The lua loader is quite mature, and /boot is getting a bit cluttered.
Allow removing the Forth loader with `make delete-old` if WITHOUT_FORTH
is set, instead of the previous behavior of only removing the doc.

MFC:			no, I think this is a breaking change
Approved by:		kevans (src)
Reviewed by:		kevans (UPDATING note tweaked since)
Discussed with:		imp, tsoome (thanks!)
Differential Revision:	https://reviews.freebsd.org/D50708

UPDATING

@@ -27,6 +27,10 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 15.x IS SLOW:
 	world, or to merely disable the most expensive debugging functionality
 	at runtime, run "ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20250625:
+	"make delete-old" will now remove the Forth bootloader entirely
+	if the system is built with WITHOUT_FORTH.
+
 20250614:
 	MIT KRB5 (MIT Kerberos5) has been imported into 15-CURRENT. To
 	and install MIT KRB5, add WITH_MITKRB5=yes to /etc/src.conf. This

tools/build/mk/OptionalObsoleteFiles.inc

@@ -1992,6 +1992,32 @@ OLD_FILES+=usr/share/man/man8/fdcontrol.8.gz
 .endif
 
 .if ${MK_FORTH} == no
+OLD_FILES+=boot/beastie.4th
+OLD_FILES+=boot/brand-fbsd.4th
+OLD_FILES+=boot/brand.4th
+OLD_FILES+=boot/check-password.4th
+OLD_FILES+=boot/color.4th
+OLD_FILES+=boot/delay.4th
+OLD_FILES+=boot/efi.4th
+OLD_FILES+=boot/frames.4th
+OLD_FILES+=boot/loader_4th
+OLD_FILES+=boot/loader_4th.efi
+OLD_FILES+=boot/loader_4th.efi.old
+OLD_FILES+=boot/loader_4th.old
+OLD_FILES+=boot/loader.4th
+OLD_FILES+=boot/logo-beastie.4th
+OLD_FILES+=boot/logo-beastiebw.4th
+OLD_FILES+=boot/logo-fbsdbw.4th
+OLD_FILES+=boot/logo-orb.4th
+OLD_FILES+=boot/logo-orbbw.4th
+OLD_FILES+=boot/menu-commands.4th
+OLD_FILES+=boot/menu.4th
+OLD_FILES+=boot/menusets.4th
+OLD_FILES+=boot/screen.4th
+OLD_FILES+=boot/shortcuts.4th
+OLD_FILES+=boot/support.4th
+OLD_LIBS+=boot/userboot_4th.so
+OLD_FILES+=boot/version.4th
 OLD_FILES+=usr/share/man/man8/beastie.4th.8.gz
 OLD_FILES+=usr/share/man/man8/brand.4th.8.gz
 OLD_FILES+=usr/share/man/man8/check-password.4th.8.gz