[llvm] [Memory] Call __clear_cache in InvalidateInstructionCache on LoongArch (PR #67285)

[Lu Weining via llvm-commits]

SixWeining wrote:

> IIRC, `__clear_cache` is DBAR, and I think we need not only DBAR but also IBAR?

`__clear_cache` has different implementations:
- gcc: `ibar 0`
- libgcc: empty (I have reported this issue to gcc loongarch maintainers)
- compiler-rt: `ibar 0`

https://github.com/llvm/llvm-project/pull/67285