sdl2: enable linux-only features (#79728)
sdl2: enable linux-only features (#79728)

Some reverse deps and some of our users expect sdl2 to be built with all of these.
We enabled these over time and people have been using these features since then.
lemzwerg/homebrew-core,stgraber/homebrew-core,zyedidia/homebrew-core,makigumo/homebrew-core,mfikes/homebrew-core,mbcoguno/homebrew-core,Linuxbrew/homebrew-core,adam-moss/homebrew-core,nandub/homebrew-core,Moisan/homebrew-core,makigumo/homebrew-core,chrisfinazzo/homebrew-core,zyedidia/homebrew-core,nandub/homebrew-core,Linuxbrew/homebrew-core,sjackman/homebrew-core,mfikes/homebrew-core,cblecker/homebrew-core,adam-moss/homebrew-core,stgraber/homebrew-core,filcab/homebrew-core,chrisfinazzo/homebrew-core,Homebrew/homebrew-core,sjackman/homebrew-core,lemzwerg/homebrew-core,mbcoguno/homebrew-core,cblecker/homebrew-core,uyjulian/homebrew-core,filcab/homebrew-core,Homebrew/homebrew-core,mbcoguno/homebrew-core,Moisan/homebrew-core,uyjulian/homebrew-core,nbari/homebrew-core,nbari/homebrew-core