libexec: Automatically generate rtld-elf list and generalise TAGS

Note that the pattern for matching is made slightly more specific, so as
to permit libcompats where one is a prefix of another (e.g. CheriBSD has
lib64 and lib64c).

Reviewed by:	brooks, jhb, emaste, imp, kib
Differential Revision:	https://reviews.freebsd.org/D41183

libexec/Makefile

@@ -3,6 +3,8 @@
 
 .include <src.opts.mk>
 
+.include <bsd.compat.pre.mk>
+
 SUBDIR=	${_atf} \
 	${_atrun} \
 	${_blacklistd-helper} \
@@ -84,7 +86,9 @@ _tftp-proxy=	tftp-proxy
 
 .if !defined(NO_PIC) && !defined(NO_RTLD)
 _rtld-elf=	rtld-elf
-SUBDIR.${MK_LIB32}+=	rtld-elf32
+.for LIBCOMPAT libcompat in ${_ALL_LIBCOMPATS_libcompats}
+SUBDIR.${MK_LIB${LIBCOMPAT}}+=	rtld-elf${libcompat}
+.endfor
 .endif
 
 .if ${MK_RBOOTD} != "no"

libexec/rtld-elf/Makefile

@@ -14,13 +14,17 @@ MK_ASAN=	no
 MK_SSP=		no
 MK_UBSAN=	no
 
+.include <bsd.compat.pre.mk>
+
 .if !defined(NEED_COMPAT)
 CONFS=		libmap.conf
 .endif
 PROG?=		ld-elf.so.1
-.if (${PROG:M*ld-elf32*} != "")
-TAGS+=		lib32
+.for _libcompat in ${_ALL_libcompats}
+.if ${PROG:M*ld-elf${_libcompat}[-.]*} != ""
+TAGS+=		lib${_libcompat}
 .endif
+.endfor
 SRCS= \
 	crtbrand.S \
 	rtld_start.S \