[llvm] [update_mir_test_checks] Add missing MIFlags (PR #150012)

[Fabian Ritter via llvm-commits]

ritter-x2a wrote:

I'm pretty sure this PR didn't change anything about the availability of `inttypes.h` on the fuchsia runner, so that failure is probably unrelated.

https://github.com/llvm/llvm-project/pull/150012