tests: Make check-block a phony target

Fixes: b93b63f5 "test makefile overhaul"
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-Id: <20190319072104.32591-1-armbru@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

tests/Makefile.include

@@ -1164,7 +1164,7 @@ check-acceptance: check-venv $(TESTS_RESULTS_DIR)
 
 # Consolidated targets
 
-.PHONY: check-qapi-schema check-qtest check-unit check check-clean
+.PHONY: check-block check-qapi-schema check-qtest check-unit check check-clean
 check-qapi-schema: $(patsubst %,check-%, $(check-qapi-schema-y)) check-tests/qapi-schema/doc-good.texi
 check-qtest: $(patsubst %,check-qtest-%, $(QTEST_TARGETS))
 check-block: $(patsubst %,check-%, $(check-block-y))