Disable -Wcast-function-type-mismatch

Code owners should fix this.
```
...re/jni/AndroidRuntime.cpp:1499:25: error: cast from 'void (*)(void *)' to 'android_thread_func_t' (aka 'int (*)(void *)') converts to incompatible function type [-Werror,-Wcast-function-type-mismatch]
 1499 |     javaCreateThreadEtc((android_thread_func_t) start, arg, name,
```

Bug: b/353528991
Flag: EXEMPT b/353528991
Test: m checkbuild
Change-Id: Id9645a6d25c030912762992ac6141ab6dffe9f61