Suggest adding arch to cache key

[andy5995]

setup-sdl/src/main.ts

Line 664 in bc89bdf

const cache_key = `setup-sdl-${project}-${project_hash}`;

Something like this I think is all that would be needed for this action to work in jobs using arm64 GitHub runners that have x64 builds in a matrix. (see error on libsdl-org/SDL_net#131)

const arch = process.arch;  // returns 'x64', 'arm64', etc.
const cache_key = `setup-sdl-${project}-${project_hash}-${arch}`; 

If you're interested, I'll submit a PR.