rpm, debian: a couple of variables to reduce diffs for pluggable modules.

debian/Makefile

diff --git a/debian/Makefile b/debian/Makefile
index 5d8a55c..3c6b650 100644
--- a/debian/Makefile
+++ b/debian/Makefile
@@ -26,6 +26,8 @@
 ARCH=		$(shell uname -m)
 NPROC=		$(shell getconf _NPROCESSORS_ONLN)
 MODSRC_PREFIX=	extra/
+MODSRC_PATH=	$(MODSRC_PREFIX)
+BUILD_DIR=	$$(BUILDDIR_nginx)
 
 MODULES=	geoip image-filter njs perl xslt
 

rpm/SPECS/Makefile

diff --git a/rpm/SPECS/Makefile b/rpm/SPECS/Makefile
index 56f3a50..a0c33bf 100644
--- a/rpm/SPECS/Makefile
+++ b/rpm/SPECS/Makefile
@@ -7,6 +7,8 @@
 BUILD_ENV_PATH=	${HOME}/rpmbuild
 MODULE_TARGET?=	oss
 MODSRC_PREFIX=
+MODSRC_PATH=	$(SRCPATH)
+BUILD_DIR=	%{bdir}
 
 ifeq ($(MODULE_TARGET), plus)
 MODULE_SPEC_TEMPLATE=	nginx-plus-module.spec.in