[lld] [LLD][COFF] Prevent to emit relocations for discarded weak wrapped symbols (PR #156214)

[via llvm-commits]

jeremyd2019 wrote:

It looks like it's still pulling in all the `__wrap_` symbols from cygwin1.dll:
```
00002220       000022b4 00000000 00000000 000029f0 0000242c

        DLL Name: cygwin1.dll
        vma:     Ordinal  Hint  Member-Name  Bound-To
        0000242c  <none>  0010  __cxa_atexit
        00002434  <none>  002f  __main
        0000243c  <none>  005d  __wrap__ZdaPv
        00002444  <none>  005e  __wrap__ZdaPvRKSt9nothrow_t
        0000244c  <none>  005f  __wrap__ZdaPvSt11align_val_t
        00002454  <none>  0060  __wrap__ZdaPvSt11align_val_tRKSt9nothrow_t
        0000245c  <none>  0061  __wrap__ZdaPvm
        00002464  <none>  0062  __wrap__ZdaPvmSt11align_val_t
        0000246c  <none>  0063  __wrap__ZdlPv
        00002474  <none>  0064  __wrap__ZdlPvRKSt9nothrow_t
        0000247c  <none>  0065  __wrap__ZdlPvSt11align_val_t
        00002484  <none>  0066  __wrap__ZdlPvSt11align_val_tRKSt9nothrow_t
        0000248c  <none>  0067  __wrap__ZdlPvm
        00002494  <none>  0068  __wrap__ZdlPvmSt11align_val_t
        0000249c  <none>  0069  __wrap__Znam
        000024a4  <none>  006a  __wrap__ZnamRKSt9nothrow_t
        000024ac  <none>  006b  __wrap__ZnamSt11align_val_t
        000024b4  <none>  006c  __wrap__ZnamSt11align_val_tRKSt9nothrow_t
        000024bc  <none>  006d  __wrap__Znwm
        000024c4  <none>  006e  __wrap__ZnwmRKSt9nothrow_t
        000024cc  <none>  006f  __wrap__ZnwmSt11align_val_t
        000024d4  <none>  0070  __wrap__ZnwmSt11align_val_tRKSt9nothrow_t
        000024dc  <none>  0079  _dll_crt0
        000024e4  <none>  0080  _impure_ptr
        000024ec  <none>  0118  calloc
        000024f4  <none>  0192  cygwin_detach_dll
        000024fc  <none>  0194  cygwin_internal
        00002504  <none>  01b0  dll_dllcrt0
        0000250c  <none>  0262  free
        00002514  <none>  03ad  malloc
        0000251c  <none>  0421  posix_memalign
        00002524  <none>  0444  printf
        0000252c  <none>  04de  realloc
```

vs this with bfd
```
00007028       000070a0 00000000 00000000 00007428 00007178

        DLL Name: cygwin1.dll
        vma:     Ordinal  Hint  Member-Name  Bound-To
        00007178  <none>  0010  __cxa_atexit
        00007180  <none>  002f  __main
        00007188  <none>  0067  __wrap__ZdlPvm
        00007190  <none>  0068  __wrap__ZdlPvmSt11align_val_t
        00007198  <none>  006d  __wrap__Znwm
        000071a0  <none>  006f  __wrap__ZnwmSt11align_val_t
        000071a8  <none>  0079  _dll_crt0
        000071b0  <none>  0080  _impure_ptr
        000071b8  <none>  0118  calloc
        000071c0  <none>  0192  cygwin_detach_dll
        000071c8  <none>  0194  cygwin_internal
        000071d0  <none>  01b0  dll_dllcrt0
        000071d8  <none>  0262  free
        000071e0  <none>  03ad  malloc
        000071e8  <none>  0421  posix_memalign
        000071f0  <none>  0444  printf
        000071f8  <none>  04de  realloc
```

<details>
<summary>Test source (no defines)</summary>

```c++
#include <stdio.h>
#include <new>
#include <string>

#ifdef OVERRIDE_NEW_DELETE
#define WIN32_LEAN_AND_MEAN
#include <windows.h>

void *operator new (std::size_t sz)
{
        printf ("In new\n");
        return LocalAlloc (LMEM_FIXED, sz);
}

void operator delete (void *p)
{
        printf ("In delete\n");
        LocalFree (p);
}

void operator delete (void *p, std::size_t)
{
        printf ("In delete sz\n");
        LocalFree (p);
}
#endif

struct alignas(32) foo {};

int main (void)
{
        char *p = new char (0); // _Znwm
        printf ("%p\n", p);
        delete p; // _ZdlPvm
        foo *bar = new foo; // _ZnwmSt11align_val_t
        printf ("%p\n", bar);
        delete bar; // _ZdlPvmSt11align_val_t

        {
                std::string foo (1024, 'x');
                printf ("%p\n", foo.data ());
        }
        return 0;
}
```
</details>

https://github.com/llvm/llvm-project/pull/156214