Building kernel, -mno-3dnow and stuff.

[Darren Pilgrim]

From: Viatcheslav Fedorov
> 
> cc -O -pipe -march=pentiumpro -march=athlon-tbird 
> -I/<...cut...>  -mno-mmx -mno-3dnow -mno-sse -mno-sse2

These are disabled because they cause problems when used in the kernel.

> my ``/etc/make.conf'' file:
> -------------------------------------
> CPUTYPE=athlon-tbird
> CFLAGS= -O -pipe -march=pentiumpro
> COPTFLAGS= -O -fomit-frame-pointer -march=pentiumpro -pipe
> -------------------------------------

You should not put -march in your FLAGS variables.  CPUTYPE determines the
correct architecture- and processor-specific compiler flags.