Build failure if USE_FORT=YES

[Aleksey Cheusov <cheusov%tut.by@localhost>]

NetBSD current and 6.0_beta fail to build if USE_FORT is set to YES in
mk.conf.  The problem is that USE_SSP used for passing
-Wno-stack-protector to CPPFLAGS is not initialized corectly.

The following patch solves the problem.
Do you mind if I commit it?

".include <bsd.own.mk>" is optional because
it is included from ../../lvm2tools.mk.

Index: external/gpl2/lvm2/lib/liblvm/Makefile
===================================================================
RCS file: /cvsroot/src/external/gpl2/lvm2/lib/liblvm/Makefile,v
retrieving revision 1.5
diff -u -U 5 -r1.5 Makefile
--- external/gpl2/lvm2/lib/liblvm/Makefile      26 May 2011 12:56:26 -0000      
1.5
+++ external/gpl2/lvm2/lib/liblvm/Makefile      28 Apr 2012 16:02:59 -0000
@@ -12,10 +12,13 @@
 CWARNFLAGS+=   -Wno-parentheses
 
 CPPFLAGS+=     -I${LVM2_DISTDIR}/lib -I${LVM2_DISTDIR}/include \
                -I. 
 
+.include <bsd.own.mk>
+.include <bsd.sys.mk> # for USE_SSP
+
 # Some parts of liblvm can't be protected because if its
 # alloca() usage.
 #
 .if defined(USE_SSP) && (${USE_SSP} != "no")
 CPPFLAGS+=     -Wno-stack-protector
Index: external/gpl2/lvm2/sbin/lvm/Makefile
===================================================================
RCS file: /cvsroot/src/external/gpl2/lvm2/sbin/lvm/Makefile,v
retrieving revision 1.10
diff -u -U 5 -r1.10 Makefile
--- external/gpl2/lvm2/sbin/lvm/Makefile        26 May 2011 12:56:26 -0000      
1.10
+++ external/gpl2/lvm2/sbin/lvm/Makefile        28 Apr 2012 16:02:59 -0000
@@ -28,10 +28,13 @@
                -I. -I${LIBDEVMAPPER_INCLUDE} -I${LVM2_DISTDIR}/tools \
                -I${LIBDEVMAPPER_DISTDIR}
 
 CPPFLAGS+=     -DLVM_SHARED_PATH=\"$(BINDIR)/lvm\"
 
+.include <bsd.own.mk>
+.include <bsd.sys.mk> # for USE_SSP
+
 # Some parts of the code can't be protected because if its
 # alloca() usage.
 #
 .if defined(USE_SSP) && (${USE_SSP} != "no")
 CPPFLAGS+=      -Wno-stack-protector