fd_fdstat_set_flags truncates file

[yagehu]

Describe the bug
If a file is opened with oflags::trunc, a call to fd_fdstat_set_flags will truncate the file.

To Reproduce

Compile this snippet with wasi-sdk and run it:

clang wazero-write.c
mkdir -p tmp
wazero run -mount tmp a.out
stat tmp/a 

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

int main(void) {
  int fd = open("tmp/a", O_RDWR | O_CREAT | O_TRUNC);
  if (fd == -1) {
    perror("open");
    return 1;
  }

  char * buf = "abc";

  int written = write(fd, buf, 3);

  printf("written %d\n", written);

  int fcntl_ret = fcntl(fd, F_SETFL, 0);
  if (fcntl_ret != 0) {
    perror("fcntl");
    return 1;
  }

  return 0;
}

Expected behavior
The file should be size 3 because we wrote 3 bytes to it. But it is size 0.

Environment (please complete the relevant information):

• Go version: 1.21.4
• wazero Version: 5796897f37852bf2042cd63959ce4ff673c4366e
• Host architecture: amd64
• Runtime mode: compiler

Additional context
Compiling the same snippet with native clang or gcc and running it will produce a 3-byte file as expected.

[evacchi]

confirmed that even with other runtimes the byte size is still 3 after stat