add a hash for linux 5.10.46

[elementc]

Hi! I'm using musl-cross-make for a robotics project with the main executable in Rust and buildroot uwipi as the OS. uwipi ships Linux 5.10 which is an LTS kernel release.

I needed Linux headers for my project, so I added 5.10 support locally. Here's a PR which adds the hash file for that release. You should double check the sha1sum, I just used what my machine checksummed from the archive when I downloaded it manually. I don't think I was being MITM'ed, but, you can never be too sure!

Thanks for this awesome project, it saved me a ton of time.

(If you got here by googling, note that Rust internally uses a 1.1.x MUSL release as of the time of writing. I had to specify away from musl-cross-make's 1.2.x version manually in my config.mak to avoid linker issues with __clock_gettime64!)