bitbake.conf: Change systemd_unitdir definition

systemd_unitdir indicates the arch independent
files which are basically scripts and unit files
and systemd wants then to be in /lib always even
when base_libdir is  /lib64, hence we have to reflect
that and not use base_libdir to define it. Otherwise
on architectures where base_libdir is lib64 e.g. ppc64
or multilibbed x86_64 this wont work

(From OE-Core rev: 50e713d4ae35f9b5f5f2a515a95d77573610d707)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/conf/bitbake.conf

@@ -31,6 +31,7 @@ export localstatedir = "${base_prefix}/var"
 export infodir = "${datadir}/info"
 export mandir = "${datadir}/man"
 export docdir = "${datadir}/doc"
+export systemd_unitdir = "/lib/systemd"
 
 # Architecture dependent paths
 export bindir = "${exec_prefix}/bin"
@@ -39,7 +40,6 @@ export libdir = "${exec_prefix}/${baselib}"
 export libexecdir = "${libdir}/${BPN}"
 export includedir = "${exec_prefix}/include"
 export oldincludedir = "${exec_prefix}/include"
-export systemd_unitdir = "${base_libdir}/systemd"
 localedir = "${libdir}/locale"
 
 # Linkage between native/cross/nativesdk layouts