[libclc] [libclc] Restore always_inline for SPIR-V targets (PR #202891)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> targets build at -O0 and never run 'opt', so helpers are no longer inlined and survive as real calls,

Which shouldn't be a problem? 

https://github.com/llvm/llvm-project/pull/202891