Adapted from [check_invalid_gs](https://gitlab.winehq.org/wine/wine/-/blob/d7a7cae2e2d1ad34af6dbefcb06fbef2f...) in signal_i386.c. This prevents crashing when the %gs register is manipulated, such as in 32-bit code on "new-style" WoW64.
"Exertus: Darkness Approaches" is a 32-bit game that triggers this crash (on WoW64), which can be downloaded from the Bugzilla page's attachments. For another example, [test.c](https://bugs.winehq.org/attachment.cgi?id=77444) can reproduce it, courtesy of Fabian Maurer from the Bugzilla comments. This will crash whether it's compiled as 32-bit or 64-bit, while it works fine on Windows.
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=57444
-- v7: ntdll: Check for invalid GS base in the 64-bit segv_handler on WoW64.