Bug#1107693: GCC 15 much slower than 14 at compiling

[Boris Kolpackov <boris@codesynthesis.com>]

Package: g++-15
Version: 15.1.0-7

I noticed that GCC 15 is much slower at compiling C++. I tested this on a
smallish C++ codebase. It compiles with GCC 14 (Debian 14.2.0-1) in 14s.
The same plain build (no debug/optimization) takes 24s with GCC 15 (Debian
15.1.0-7).

I didn't hear any widespread outcry about such a slowdown so I am suspecting
this is something Debian-specific. Perhaps it's a checked build of GCC? If
so, maybe it makes sense to change that, seeing it's not a pre-release of
GCC?