lib{c,thr}: add DT_RUNPATH for gcc -m32

To allow gcc -m32 to work, link libc and libthr with --rpath-/usr/lib32.
When called with -m32, gcc is currently unable to communicate to
the bfd linker that it should look in /usr/lib32 to resolve needed (as
opposed to explicitly linked) libraries so we need to provide a hint.

See also: https://sourceware.org/bugzilla/show_bug.cgi?id=31395

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D43910

lib/libc/Makefile

@@ -63,6 +63,11 @@ CFLAGS+= -ftls-model=initial-exec
 LDFLAGS+= -nodefaultlibs
 LIBADD+=	compiler_rt
 LIBADD+=	sys
+.if defined(COMPAT_libcompat)
+# XXX: work around gcc -m32 + bfd ld path issue for DT_NEEDED symbols.
+# https://sourceware.org/bugzilla/show_bug.cgi?id=31395
+LDFLAGS+=	-Wl,--rpath=/usr/lib${COMPAT_libcompat}
+.endif
 
 LDFLAGS+=-Wl,--auxiliary,libsys.so.7
 

lib/libthr/Makefile

@@ -8,6 +8,11 @@ PACKAGE=	clibs
 SHLIBDIR?= /lib
 
 LIBADD=	c sys
+.if defined(COMPAT_libcompat)
+# XXX: work around gcc -m32 + bfd ld path issue for DT_NEEDED symbols.
+# https://sourceware.org/bugzilla/show_bug.cgi?id=31395
+LDFLAGS+=	-Wl,--rpath=/usr/lib${COMPAT_libcompat}
+.endif
 
 .include <src.opts.mk>
 MK_SSP=	no