Allow building when ~/.rpmmacros sets the %{_topdir}

diff --git a/packaging/Makefile.fedora b/packaging/Makefile.fedora
index 8fd0e05..11bafce 100644
--- a/packaging/Makefile.fedora
+++ b/packaging/Makefile.fedora
@@ -7,6 +7,8 @@ MYTMPDIR:=${shell mktemp -d --tmpdir=`pwd`/.. tmp_XXXXXX}
 
 WORKDIR:=${MYTMPDIR}/${HEKAFS}
 
+_TOPDIR:=${shell rpm --eval "%{_topdir}"}
+
 GLUSTERFS_RPM_VERSION:=${strip ${shell rpm -q glusterfs}}
 
 ifneq  "${GLUSTERFS_RPM_VERSION}" "package glusterfs is not installed"
@@ -19,9 +21,11 @@ MACHINE:=${shell uname -m}
 
 .PHONY: all
 
-all: ~/rpmbuild package cleanup
+all: rpmbuild package cleanup
+
+.PHONY: rpmbuild
 
-~/rpmbuild:
+rpmbuild:
 	rpmdev-setuptree
 
 .PHONY: package
@@ -52,9 +56,9 @@ package:
 	cd ${WORKDIR} && ${RM} config.sub && ln -s /usr/share/libtool/config/config.sub .
 	cd ${WORKDIR} && ${RM} missing && ln -s /usr/share/libtool/config/missing .
 	cd ${WORKDIR} && ${RM} install-sh && ln -s /usr/share/libtool/config/install-sh .
-	cd ${MYTMPDIR} && tar czf ~/rpmbuild/SOURCES/${HEKAFS}.tgz ${HEKAFS}
-	cp ${WORKDIR}/hekafs.spec ~/rpmbuild/SPECS/
-	cd ~/rpmbuild && rpmbuild -bs SPECS/hekafs.spec
+	cd ${MYTMPDIR} && tar czf ${_TOPDIR}/SOURCES/${HEKAFS}.tgz ${HEKAFS}
+	cp ${WORKDIR}/hekafs.spec ${_TOPDIR}/SPECS/
+	rpmbuild -bs ${_TOPDIR}/SPECS/hekafs.spec
 
 .PHONY: cleanup