make: add new target `package-static` to .pack.mk

This target is a wrapper on the command to build DEB and RPM packages
with a statically compiled Tarantool binary inside. It just runs the
`./static-build/make_packages.sh` script with the properly defined
VERSION env variable.

Example of usage:

    $ make -f .pack.mk package-static

NO_DOC=make
NO_TEST=make
NO_CHANGELOG=make

.pack.mk

@@ -47,6 +47,15 @@ package: prepare
 	PRESERVE_ENVVARS="TARBALL_EXTRA_ARGS,${PRESERVE_ENVVARS}" \
 	./packpack/packpack
 
+package-static:
+	if [ -n "${GIT_TAG}" ]; then \
+		export VERSION="$$(echo ${GIT_TAG} | sed 's/-/~/')"; \
+	else \
+		export VERSION="$$(echo ${GIT_DESCRIBE} | sed ${SED_REPLACE_VERSION_REGEX} | sed 's/-/~/').dev"; \
+	fi; \
+	echo VERSION=$${VERSION}; \
+	./static-build/make_packages.sh
+
 deploy:
 	if [ -z "${REPO_TYPE}" ]; then \
 		echo "Env variable 'REPO_TYPE' must be defined!"; \