Don't try to load ci.erlang.mk when testing packages

[ci skip]

test/Makefile

@@ -126,7 +126,7 @@ $(eval $(foreach t,$(patsubst %.mk,%,$(patsubst plugin_%,%,$(wildcard plugin_*.m
 # Packages.
 
 PACKAGES = $(foreach pkg,$(sort $(wildcard ../index/*.mk)),$(notdir $(basename $(pkg))))
-EXCLUDE_FROM_CHECK = [hexer_mk, inaka_mk, rabbitmq_codegen]
+EXCLUDE_FROM_CHECK = ['ci.erlang.mk', hexer_mk, inaka_mk, rabbitmq_codegen]
 
 packages: $(addprefix pkg-,$(PACKAGES))