Re: incremental bulds from scratch with beinstall.sh

Same context of WITH_META_MODE, it will speed up for sure my builds,
tunning what parts/targets of llvm will be built:


> WITH_LLVM_TARGET_AARCH64=
> WITH_LLVM_TARGET_ARM=
> WITHOUT_LLVM_TARGET_MIPS=
> WITHOUT_LLVM_TARGET_POWERPC=
> WITHOUT_LLVM_TARGET_RISCV=
> WITHOUT_LLVM_TARGET_X86=
>

I will use instead the bellow:


> WITHOUT_LLVM_TARGET_ALL=
>

and check for results, plus

WITHOUT_CLANG_FULL=


for extra tunning.


> > May be I've guess wrong about what you mean by "clean
> > /usr/obj"?
>

When I did say it I was talking about plain builds after `rm -fr
/usr/obj/*`, but it is out of context anyway. The context is METAMODE.

Other thing, I'm wandering how DIRDEPS will perform over METAMODE when we
do a buildworld/buildkernel with same src/obj on a new BE.
First I will do the llvm tunning and one of these days I will try DIRDEPS
and see how it goes.

Thanks!