[compiler-rt] pass target triple to `check_assembler_flag` (PR #188521)

[Andrew Marshall via llvm-commits]

planetmarshall wrote:

> LGTM, thank you!
> 
> Now you point this out, I have no idea why it _did_ work for me. Possibly the clang I was using was configured with Arm as its default target triple?

Yes I suspect that's probably why - there are so many ways to configure Clang I'm sure some things fall through the cracks. Thanks for the quick review!

https://github.com/llvm/llvm-project/pull/188521