Rollup merge of #132150 - taiki-e:ppc64-freebsd-abi, r=pnkfelix

Fix powerpc64 big-endian FreeBSD ABI

Note that FreeBSD version bump may be reverted due to rust-lang/rust#120869 (comment). We may want to wait to merge this until that discussion is complete.

Fixes rust-lang/rust#120869 (comment)

> > PPC64 FreeBSD (ELFv1 and ELFv2, version 13.2)
>
> It seems odd that ELFv1 and 13.N coexist.
>
> https://www.freebsd.org/releases/13.0R/relnotes/
>
> > powerpc64 switched to ELFv2 ABI at the same time it switched to LLVM. This brings us to a parity with modern Linux distributions. This also makes the binaries from previous FreeBSD versions incompatible with 13.0-RELEASE. Kernel still supports ELFv1, so jails and chroots using older FreeBSD versions are still compatible. [e4399d169acc](https://cgit.freebsd.org/src/commit/?id=e4399d169acc)
>
> Well, it is also odd that this target claims ELFv2 support since our ABI code does not use ELFv2 on this target.
>
> https://github.com/rust-lang/rust/blob/be01dabfefd2daa4574b974f571c7852085d60cb/compiler/rustc_target/src/callconv/powerpc64.rs#L102-L111

````````@rustbot```````` label +O-PowerPC +O-freebsd

Author: matthiaskrgr