[build] Makefile: throw an error when trying to build SHARED library

[sleeptightAnsiC]

[see linked issue for more context]

When asking Makefile to create SHARED library for WEB

~/raylib/src $ 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 which fixes this issue.

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: #4717

[Peter0x44]

I don't think this should be a fatal error, since that just causes inconsistency. A warning alone is fine.

[sleeptightAnsiC]

I've mentioned why this is inconsistent @Peter0x44

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

The fact that Cmake is not erroring here is also bad BUT since people usually depend on raylib with add_library(raylib) it won't be a fatal issue in 99% cases since Cmake is doing any heavy lifting.

Makefile cannot automatically do this, it can't recover on its own. If you have a build recipe that expects .so and raylib produces .a, you may get a very nasty issue somewhere down the line that won't be obvious to fix. For example, it may grab old .so that wasn't build for WEB and emcc may freak out throwing linking errors OR WORSE: it could link just fine but break at runtime.

[raysan5]

@sleeptightAnsiC I agree with @Peter0x44 that a warning is enough.

[raysan5]

@sleeptightAnsiC Merging and reviewing it myself as a warning. Thanks for the improvement.