kbuild: fix the binrpm-pkg target to work with KBUILD_OUTPUT set

The binrpm-pkg target (binary RPM only) fails when called with
KBUILD_OUTPUT set. This patch makes it work.

For the rpm-pkg target (source + binary RPM), building with
KBUILD_OUTPUT set is not possible and also not needed as the
actual build is done in a temporary directory anyway, so check
that KBUILD_OUTPUT is not set in that case to avoid later errors.

Signed-off-by: Frans Pop <elendil@planet.nl>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/scripts/package/mkspec b/scripts/package/mkspec
index 3d93f8c..47bdd2f 100755
--- a/scripts/package/mkspec
+++ b/scripts/package/mkspec
@@ -70,7 +70,7 @@
 echo 'mkdir -p $RPM_BUILD_ROOT/lib/firmware'
 echo "%endif"
 
-echo 'INSTALL_MOD_PATH=$RPM_BUILD_ROOT make %{_smp_mflags} modules_install'
+echo 'INSTALL_MOD_PATH=$RPM_BUILD_ROOT make %{_smp_mflags} KBUILD_SRC= modules_install'
 echo "%ifarch ia64"
 echo 'cp $KBUILD_IMAGE $RPM_BUILD_ROOT'"/boot/efi/vmlinuz-$KERNELRELEASE"
 echo 'ln -s '"efi/vmlinuz-$KERNELRELEASE" '$RPM_BUILD_ROOT'"/boot/"