[compiler-rt] [compiler-rt][test] Remove noisy warnings (PR #191510)

[Dan Liew via llvm-commits]

delcypher wrote:

This seems a little confusing

```
  "target_triple": "x86_64-unknown-linux-gnu",
  "target_arch": "i386",
  "target_cflags": " -Wthread-safety -Wthread-safety-reference -Wthread-safety-beta ",
  "host_arch": "x86_64",
```

Why is the target triple not set to `i386-unknown-linux-gnu`? Relying on the `-m32` flag instead of just setting the target triple appropriately doesn't seem ideal.

https://github.com/llvm/llvm-project/pull/191510