Support -lSDL2_mixer and others

[kripken]

Background: emscripten-ports/SDL2_mixer#2

Things like -lSDL2 work because the internal library name matches the flag. But SDL2_mixer has a different internal name, with _ogg as a suffix, which prevents this.

The internal name is important as we build a different SDL2_mixer depending on the codecs. But it makes simple link flags not work.

It would be good to make such link flags just work, perhaps by mapping -l names to the internal ones. This would require some changes in emcc.py and related code's handling of link flag libraries, and maybe also the ports code itself like tools/ports/sdl2_mixer.py.

[sbc100]

One possiblity it so have many different version of libSDL2_mixer.a but have the directory name distinguish them.

So

• ogg/libSDL2_mixer.a
• ogg_mp3/libSDL2_mixer.a

Then SDL2_MIXER_OGG would add -L<path_to_system_libs>/ogg to the library path?

Basically would move variant from the library name to the library path.

[Beuc]

I confirm this broke my pygame_sdl2 build.
wasm-ld: error: unable to find library -lSDL2_mixer

However I have troubles determining when that broke. My build worked in 2.0.2 but the related SDL2_mixer changes seem to predate.

[sbc100]

I believe it was when SDL_mixer to split into multiple different libraries with different names. Maybe #11577? But yes that would have been way back in 1.39.20.

You say it worked for you in 2.0.2, can you check 2.0.3?