[Geronymos]

Fixes #6315.

I choose ../../examples/core/raygui.h as a path for raygui because it seems most generic.

[raysan5]

@Geronymos raygui path should be provided externally and not hardcoded this way, merging for convenience but definitely not the right solution

[Geronymos]

Another solution might be to delete the dependency of raygui_api.$(EXTENSION) from the phony parse target. Or remove the raygui and reasings_api targets all together, since they are only included in the examples directory (the path for reasings_api also doesn't exist anymore but isn't a dependecy of the parse target either). And maybe expand the comment, that these should be provided externally or generated by executing rlparser directly with the correct command-line arguments instead.