GCC -Wstringop-truncation due to safe_strcpy()

MDEV-34266 removed a #pragma that would silence a GCC warning about possible missing NUL terminator when invoking strncpy(). It looks like the warning depends on some optimization settings.

Initially I thought that the warning got smarter in GCC 14, which was recently made the default compiler in Debian Sid, but I found examples of the warnings in the build logs also with GCC 12.2.0.