GCC15: Typos in gcc/BASE-VER

[Chris Clayton via Gcc]

Hi

Commit 017c45fa2a4da40893f0aacd96164f04c78cb245 bumped BASE-VER to 15.0.1, but 
the commit message says it's been bumped
to 14.0.1. I guess it will obvious to readers that it's a typo, but want to fix 
it.44.

Chris