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

[Wenju He via cfe-commits]

https://github.com/wenju-he approved this pull request.

LGTM, please update PR title and message accordingly.

`-disable-llvm-passes` should be better than `-O0`.
SPIRV is generic target and doesn't have TTI interface, which can cause optimizations pass to make suboptimal decisions. An alternative approach is to selectively disable some passes , but this is not trivial.

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