Update builtin libraries linking flags

GCC 15.2.0 release

Update builtin libraries linking flags

GCC 12.5.0 release

FreeBSD

GCC 13.4.0 release

GCC 14.3.0 release

Defaults to short wchar_t

This allows the newlib mb2wc series API to work directly with besta UTF16 types, without the nowide hack. This technically breaks EABI compatibility but simplifies the libc setup a lot, and int wchar_t support can be opted-in again by using -fno-short-wchar.

GCC 15.1.0 release

GCC 16 basepoint