Fix a new warning on Cygwin

Fix a new warning on Cygwin

> ../../gdb/windows-nat.c: In function ‘windows_solib* windows_make_so(const char*, LPVOID)’:
> ../../gdb/windows-nat.c:714:12: error: declaration of ‘char name [512]’ shadows a parameter [-Werror=shadow=compatible-local]
>   714 |       char name[SO_NAME_MAX_PATH_SIZE];
>       |            ^~~~
> ../../gdb/windows-nat.c:655:30: note: shadowed declaration is here
>   655 | windows_make_so (const char *name, LPVOID load_addr)
>       |                  ~~~~~~~~~~~~^~~~