[clang] [llvm] Finish deleting the le32/le64 targets (PR #98497)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> It looks like the removal missed a few bits: PNaClABIBuiltinVaList and clang/lib/CodeGen/Targets/PNaCl.cpp weren't removed.

I was under the impression those bits were still needed for Chromium. CC @dschuff 

> > Unfortunately, this utterly breaks Halide, which was in fact relying on both of these targets.
> 
> We can temporarily revert this, but we aren't going to leave the orphaned remains of PNaCl in-tree forever. If you need a "halide" target long-term, please write up a proposal on Discourse describing exactly what bits you need, why you need them, relevant test coverage in-tree and out-of-tree, and a proposed code owner for those bits.

I'm comfortable with a second temporary revert if it's necessary so long as there's a time limit attached to it. The first attempted removal was over three years ago, so if Halide needs this target beyond Clang 20 (roughly six months from now), I think that they need to come to the community with a new proposed timeline for removal or a proposal for official target support of some kind (which requires additional maintenance beyond what the status quo is -- this target has very little in the way of testing or documentation).

https://github.com/llvm/llvm-project/pull/98497