I want to declare my wildcard target as phony, but phony doesn\'t support wildcards:
My makefile:
%.config:
gcc <>
These are conflicting aims. A phony target is one that doesn't correspond to a real file. In your case, the file exists, but it's not really a target.
I would suggest not using the name of the config file as the target. Instead, construct a system based on one of the following:
make something_else
make CONFIG=something_else.config