Prepare build system to produce RPMs

Add .spec file under extras/rpms and create targets to produce
source and binary rpms

extras/rpm/Makefile.in

@@ -0,0 +1,35 @@
+TARBALL=$(shell realpath ../../build-root/clixon-latest.tar.xz)
+BASENAME=$(shell basename $(TARBALL) | sed -e s/.tar.\*//)
+VERSION=$(shell echo $(BASENAME) | cut -f2 -d-)
+RELEASE=$(shell echo $(BASENAME) | cut -f3- -d- | sed -e s/-/_/g)
+BR=$(shell realpath $(CURDIR)/../../build-root)
+RPMBUILD=$(BR)/rpmbuild
+
+all: RPM
+
+spec:
+	@echo $(TARBALL)
+	mkdir -p $(RPMBUILD)/{RPMS,SRPMS,BUILD,SOURCES,SPECS}
+	cp $(TARBALL) $(RPMBUILD)/SOURCES/clixon-$(VERSION)-$(RELEASE).tar.xz
+	cp clixon.spec $(RPMBUILD)/SPECS
+
+srpm: spec
+	rpmbuild -bs \
+	  --define "cligen_prefix @CLIGEN_PREFIX@" \
+	  --define "_topdir $(RPMBUILD)" \
+	  --define "_version $(VERSION)" \
+	  --define "_release $(RELEASE)" \
+	  $(RPMBUILD)/SPECS/clixon.spec
+	mv $$(find $(RPMBUILD)/SRPMS -name \*.src.rpm -type f) $(BR)
+
+# Define DEVELOPER environmrnt variable to prevent .spec to add cligent to the
+# list of build requirements
+RPM: spec
+	rpmbuild -bb \
+	  --define "cligen_prefix @CLIGEN_PREFIX@" \
+	  $${DEVELOPER:+--define "developer yes"} \
+	  --define "_topdir $(RPMBUILD)" \
+	  --define "_version $(VERSION)" \
+	  --define "_release $(RELEASE)" \
+	  $(RPMBUILD)/SPECS/clixon.spec
+	mv $$(find $(RPMBUILD)/RPMS -name \*.rpm -type f) $(BR)