[compiler-rt] [TSan] Add lock_during_write flag on Apple platforms to avoid deadlock (PR #157928)

[Dan Blackwell via llvm-commits]

DanBlackwell wrote:

Note: I've tested the following on Ubuntu to see if the same thing can happen:

```
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#ifdef SHARED_LIB
#include <dlfcn.h>
#include <stdlib.h>
#include <pthread.h>

pthread_mutex_t mtx;

typedef ssize_t (*func_t)(int, const void *, size_t);

extern "C" ssize_t write(int fd, const void *buf, size_t count) {
    static func_t write_real = NULL;
    write_real = (func_t)dlsym(RTLD_NEXT, "write");
    pthread_mutex_lock(&mtx);
    printf("Intercepted\n");
    pthread_mutex_unlock(&mtx);
    return write_real(fd, buf, count);
}

#else

int main() {
    write(1, "test", 4);
    return 0;
}

#endif
```

>From what I can tell, any calls within the `write` wrapper here (`pthread_mutex_lock`) don't get intercepted by TSan; thus it can't deadlock in the same way as Apple can with interposition. I will keep this flag as Apple only, as it solves a problem that is Apple specific.

https://github.com/llvm/llvm-project/pull/157928