[lld] [LLD] [MinGW] Fall back to using default target if no -m flag given. (PR #134700)

[via llvm-commits]

jeremyd2019 wrote:

test source:
```c
#include <assert.h>
#include <stdio.h>
#include <winsock2.h>
#include <windows.h>

__attribute__((__used__))
const IMAGE_LOAD_CONFIG_DIRECTORY _load_config_used = {
  .Size = sizeof(_load_config_used),
  .GuardFlags = 0x3000, /*IMAGE_GUARD_PROTECT_DELAYLOAD_IAT|IMAGE_GUARD_DELAYLOAD_IAT_IN_ITS_OWN_SECTION*/
};

int global_var = 42;

int main(void) {
  unsigned short ret;
  setvbuf(stdout, NULL, _IONBF, 0);
  printf("MAIN: starting\n");
  printf("MAIN: incremented global var = %d\n", ++global_var);
  printf("MAIN: about to call htons\n");
  ret = htons(0x1234);
  printf("MAIN: htons returned %hx\n", ret);
  printf("MAIN: incremented global var = %d\n", ++global_var);
  printf("MAIN: OK\n");
  return 0;
}
```

build with
```
clang -fuse-ld=lld -o main.exe main.c -lws2_32 -Wl,-delayload,WS2_32.dll
```

main.exe crashes when the loader tries to set up TLS stuff, which is now in a read-only page apparently.

https://github.com/llvm/llvm-project/pull/134700