[llvm] [libc][bazel] Add Bazel rules for rand/srand functions. (PR #159617)

[Alexey Samsonov via llvm-commits]

vonosmas wrote:

> If this is only for internal it would probably be better to make an internal randomness function that takes the state as an argument instead of it being a global. I already do that in a few places.

Good point. Yes, the file in question is `libc/test/src/math/FmaTest.h`, and I agree it's probably worth migrating it to internal RNG rather than use `LIBC_NAMESPACE::(s)rand` directly (you even had to fix it on GPU in 71ffc1f0ea1c64d475d9248ea7c68dfec16ee1ab). I'll check w/ @lntue  , but this can be done independently or rand/srand Bazel support.

https://github.com/llvm/llvm-project/pull/159617