[llvm] [RISCV] Run MakeCompresible at Os as well (PR #207172)

[Alex Bradbury via llvm-commits]

asb wrote:

Do you have any figures for the impact on compile time or the runtime performance of produced binaries when doing this? I could certainly believe this makes sense, but it would be good to have the data.

https://github.com/llvm/llvm-project/pull/207172