Fix armv7-sony-vita-newlibeabihf LLVM target triple

[madsmtm]

It was previously normalized by LLVM to thumbv7a-vita-unknown-eabihf (can be seen with clang -target thumbv7a-vita-eabihf -v), which seems wrong, as Vita is the OS name.

Motivation: To make it easier to verify that cc-rs' conversion from rustc to Clang/LLVM triples is correct.

CC target maintainers @nikarh, @pheki and @zetanumbers.
r? jieyouxu

[rustbot]

These commits modify compiler targets.
(See the Target Tier Policy.)

[madsmtm]

Another thing to consider: Is thumbv7a the correct arch to pass to LLVM, or should it actually be armv7 like the target name?

[jieyouxu]

This seems to be basically if the target maintainers agree with this change, so please r=me if they do.
@bors delegate+ rollup

[bors]

✌️ @madsmtm, you can now approve this pull request!

If @jieyouxu told you to "r=me" after making some further change, please make that change, then do @bors r=@jieyouxu

[jieyouxu]

@rustbot blocked (waiting to hear back from target maintainers, not much for me or PR author to do)

[pheki]

Interestingly some docs from Clang indicate that the vendor is optional but sys not so much: "The vendor needs to be specified only if there’s a relevant change, for instance between PC and Apple. Most of the time it can be omitted (and Unknown) will be assumed, which sets the defaults for the specified architecture. The system name is generally the OS (linux, darwin), but could be special like the bare-metal “none”."

That said, I'm personally fine with this change with one caveat: sony does not seem to be a valid target for LLVM[0] [1], it seems like they use SCEI for the PS4 and PS5, so that would probably make more sense. I checked for LLVM code checking for SCEI specifically and they don't seem to have any special cases that would affect us, so this probably wouldn't break anything.

[zetanumbers]

I have originally used bare-metal llvm target arm7a-unknown-none or something like that, cause there's no vita support in clang. thumb7a was intentional, assuming such llvm target is sound.

[madsmtm]

Interestingly some docs from Clang indicate that the vendor is optional but sys not so much: "The vendor needs to be specified only if there’s a relevant change, for instance between PC and Apple. Most of the time it can be omitted (and Unknown) will be assumed, which sets the defaults for the specified architecture. The system name is generally the OS (linux, darwin), but could be special like the bare-metal “none”."

Yeah, arguably the invalid normalization could be a LLVM bug?

I picked sony because that's what's passed by the mipsel-sony-psp/mipsel-sony-psx targets, and because LLVM is fine with invalid/unknown target vendors (and this does allow a forked LLVM to handle it differently if it wants to).

I'm fine with arm7a-unknown-none-eabihf or something else instead if that's what you prefer (though I do think it'd be nice if it was consistent with the other sony targets).

[pheki]

thumbv7a is probably better as it is a thumb processor this target has thumb mode enabled. I'm personally in favor of either thumbv7a-sony-vita-eabihf or thumbv7a-scei-vita-eabihf in case we ever need to fork / contribute to llvm.

Edit: fixed target names