[Support] Use zx_cache_flush on Fuchsia to flush instruction cache

Fuchsia doesn't use __clear_cache, instead it provide zx_cache_flush
system call. Use it to flush instruction cache.

Differential Revision: https://reviews.llvm.org/D47753

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@334068 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed