Introduce a new make variable: NMFLAGS.

As the name indicates, these are flags to pass to nm(1).  The newer
binutils have a plugin mechanism so, to build something with LLVM's
LTO, we need to pass flags to nm(1).  This commit also extends
lorder(1) to pass NMFLAGS to nm(1).

share/mk/sys.mk

@@ -167,6 +167,7 @@ MAKE		?=	make
 
 .if !defined(%POSIX)
 NM		?=	nm
+NMFLAGS		?=
 
 OBJC		?=	cc
 OBJCFLAGS	?=	${OBJCINCLUDES} ${CFLAGS} -Wno-import

usr.bin/lorder/lorder.1

@@ -28,7 +28,7 @@
 .\"     @(#)lorder.1	8.2 (Berkeley) 4/28/95
 .\" $FreeBSD$
 .\"
-.Dd October 25, 2006
+.Dd August 14, 2015
 .Dt LORDER 1
 .Os
 .Sh NAME
@@ -68,6 +68,9 @@ Path to the
 .Xr nm 1
 binary, defaults to
 .Dq Li nm .
+.It Ev NMFLAGS
+Flags to pass to
+.Xr nm 1 .
 .El
 .Sh EXAMPLES
 .Bd -literal -offset indent

usr.bin/lorder/lorder.sh

@@ -60,7 +60,7 @@ done
 #
 # if the line has " U " it's a globally undefined symbol, put it into
 # the reference file.
-${NM} -go $* | sed "
+${NM} ${NMFLAGS} -go $* | sed "
 	/ [TDW] / {
 		s/:.* [TDW] / /
 		w $S