Fix(WEB): Makefile: throw an error when trying to build SHARED library
When asking Makefile to create SHARED library for WEB
$ make TARGET_PLATFORM=PLATFORM_WEB RAYLIB_LIBTYPE=SHARED
it would instead silently create STATIC library
thus not fulfilling the request as expected
This commit adds an error in this case and stops further execution.
This is not consistent with Cmake, because Cmake throws the warning and
does not stop, but Cmake can easily recover from this case and people
probably does not even notice it. However, Makefile is something that
you have to handle yourself and you have to recover from any issues so
having an error and aborting with exit code 1 is more expected.
Otherwise people may spend a lot of time debugging Makefile in order to
understand what's even going on.
Fixes: https://github.com/raysan5/raylib/issues/4717