rpm/Makefile: use DISTROS intermediate variable, similar to deb

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit ad03155)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Upstream-commit: 978232d2b9215ca2c112417e10f247409f82b61a
Component: packaging

Author: thaJeztah

components/packaging/rpm/Makefile

@@ -41,6 +41,7 @@ SOURCES=$(addprefix rpmbuild/SOURCES/, $(SOURCE_FILES))
 
 FEDORA_RELEASES := fedora-31 fedora-30 fedora-29 fedora-28
 CENTOS_RELEASES := centos-7
+DISTROS := $(FEDORA_RELEASES) $(CENTOS_RELEASES)
 
 .PHONY: help
 help: ## show make targets
@@ -60,8 +61,8 @@ fedora: $(FEDORA_RELEASES) ## build all fedora rpm packages
 .PHONY: centos
 centos: $(CENTOS_RELEASES) ## build all centos rpm packages
 
-.PHONY: $(FEDORA_RELEASES) $(CENTOS_RELEASES)
-$(FEDORA_RELEASES) $(CENTOS_RELEASES): $(SOURCES)
+.PHONY: $(DISTROS)
+$(DISTROS): $(SOURCES)
 	@echo "== Building packages for $@ =="
 	$(CHOWN) -R root:root rpmbuild
 	$(BUILD)