jit: disable ASAN for arm64 SIMD helper

[carenas]

Technically a false positive, but it might be easier to prevent it by going at the source this way.

Fixes: #302

[zherczeg]

What is the effect? It disables something at compile time?

[carenas]

Yes; ASAN works by adding "interceptor" routines in the code at build time, so this tells it not to do that for this function.