15.0 LONG buildworld time

I just upgraded one of my machines to 15.0 for testing some USB related 
work (see other thread), and one thing I noticed was that AFTER 
upgrading to 15.0 build times *doubled*.  This is unusual since the 
*first* build is typically the longest since it has to build the new 
toolchain before compiling, and after that it just uses the system build 
chain.


In my case the build time (single threaded) was 38,000 seconds on 14.2, 
however after rebooting and doing a second build it shot to 76,000 
seconds (about) -- I had rebuilt a second time since I thought the 
existence of a 14.2 library for SSL at build time contaminated the 
build, it didn't, but an error I got at startup from unbound made me 
think it did.


It seems the GENERIC kernel in the 15.0 branch has some extra debugging 
and validation, but builds shouldn't be primarily kernel limited should 
they?  Build options are mostly stock, I add -O2, and REPTOLINE options, 
and set CPU type to my native (raptorlake).  Nothing else of note, and 
certainly have never had any other issues.