lld-link (COFF): crash (STATUS_ACCESS_VIOLATION in AVX NT memset) with /FILEALIGN:1 /MERGE:.text=.data Regression in LLVM 21.1.0-rc1

## Summary
lld-link crashes with STATUS_ACCESS_VIOLATION when /FILEALIGN:1 and /MERGE:.text=.data are used together. ~~This is a regression introduced in 22.1.0; 21.1.8 (Previous version shipped with VS) links successfully with the same inputs.~~ **EDIT: it might have been 20.1.8, still checking which version works** EDIT2: 20.1.8 works 21.1.8 does not, crash happens in [**LLVM 21.1.0-rc1**](https://github.com/llvm/llvm-project/releases/tag/llvmorg-21.1.0-rc1)

Crash seems to happen after 160 bytes zeroed with vmovntdq

BT from 22.1.3:
```
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
Stack dump:
0. Program arguments: "C:\\Program Files\\Microsoft Visual Studio\\18\\Insiders\\VC\\Tools\\Llvm\\x64\\bin\\lld-link.exe" @D:\\DM40RE_native\\bisect\\build\\link_ltoobj.rsp
Exception Code: 0xC0000005
#0 0x00007ff6a28db7cb (C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Tools\Llvm\x64\bin\lld-link.exe+0x1b3b7cb)
#1 0x00007ff6a16068a5 (C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Tools\Llvm\x64\bin\lld-link.exe+0x8668a5)
#2 0x00007ff6a15fa590 (C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Tools\Llvm\x64\bin\lld-link.exe+0x85a590)
#3 0x00007ff6a143e5eb (C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Tools\Llvm\x64\bin\lld-link.exe+0x69e5eb)
#4 0x00007ff6a1431ddb (C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Tools\Llvm\x64\bin\lld-link.exe+0x691ddb)
#5 0x00007ff6a1431335 (C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Tools\Llvm\x64\bin\lld-link.exe+0x691335)
#6 0x00007ff6a0dccbc0 (C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Tools\Llvm\x64\bin\lld-link.exe+0x2cbc0)
#7 0x00007ff6a0dcc1c3 (C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Tools\Llvm\x64\bin\lld-link.exe+0x2c1c3)
#8 0x00007ff6a28a282c (C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Tools\Llvm\x64\bin\lld-link.exe+0x1b0282c)
#9 0x00007ffa38b117b3 (C:\WINDOWS\System32\KERNEL32.DLL+0x317b3)
#10 0x00007ffa3977fd00 (C:\WINDOWS\SYSTEM32\ntdll.dll+0x5fd00)
```

Repro:

```c
unsigned int startmain() { return 0; }
```
FLAGS:
```
clang-cl /c repro.c
lld-link repro.obj /SUBSYSTEM:WINDOWS /MACHINE:X64 /ENTRY:startmain /NODEFAULTLIB /FILEALIGN:1 /MERGE:.text=.data
```
Only with the combination of `/FILEALIGN:1` `/MERGE:.text=.data` the crash occurs, separately the crash doesn't occur and it gets linked sucessfully

Start with the minimal repro in repro.c and run the listed clang-cl and lld-link commands, comparing the combined /FILEALIGN:1 and /MERGE:.text=.data flags with each flag separately. Investigate the lld-link crash around the reported AVX NT memset path; done means the combination links successfully without STATUS_ACCESS_VIOLATION and the regression is covered by an appropriate test.

Written by the indexing model from the issue text.