HEADS UP: plan to switch many ports over to GCC 12 soon

hi folks.


just a heads up that i plan to switch most ports over to GCC 12
in the coming week.

at least, arm64, x86, sparc*, ia64, and riscv targets very soon,
with arm32 and alpha probably soon after.   more testing needed
for m68k, ppc, mips, and hppa.  vax needs the gcc12 version of
the Kalvis fixes, sh3 seems pretty bad off.


.mrg.