Adjusting BUILDLINK_LIBDIRS.${_pkg_} to fix build issues on 64bit linux

[David Brownlee <abs%absd.org@localhost>]

The following permits my Centos x86_64 system to successfully build
packages such as rrdtool, and does not have side effects on non
64bit+Linux systems. Does anyone have any objections to it being
committed?

Index: mk/buildlink3/bsd.buildlink3.mk
===================================================================
RCS file: /cvsroot/pkgsrc/mk/buildlink3/bsd.buildlink3.mk,v
retrieving revision 1.208
diff -u -r1.208 bsd.buildlink3.mk
--- mk/buildlink3/bsd.buildlink3.mk   2 May 2010 18:32:29 -0000    1.208
+++ mk/buildlink3/bsd.buildlink3.mk   22 Sep 2010 21:19:45 -0000
@@ -356,7 +356,11 @@
ÂBUILDLINK_LDFLAGS.${_pkg_}?= Â # empty
ÂBUILDLINK_LIBS.${_pkg_}?= Â Â Â# empty
ÂBUILDLINK_INCDIRS.${_pkg_}?= Â include
+.if ${OPSYS} == "Linux"
+BUILDLINK_LIBDIRS.${_pkg_}?= Â lib
+.else
ÂBUILDLINK_LIBDIRS.${_pkg_}?= Â lib${LIBABISUFFIX}
+.endif
Â. Âif !empty(BUILDLINK_DEPMETHOD.${_pkg_}:Mfull)
ÂBUILDLINK_RPATHDIRS.${_pkg_}?= ${BUILDLINK_LIBDIRS.${_pkg_}}
Â. Âelse