Add DevkitPPC support

[DarkKirb]

DevkitPPC is the de-facto Homebrew development kit for the Nintendo Gamecube, Wii and Wii U consoles. It is based on a gcc+binutils+newlib toolchain.

This pull request adds initial support for these 3 consoles.

DevkitPPC does not support unix-style sockets natively, meaning that bindings
to these functions was removed for powerpc targets with "nintendo" as
vendor

Suggested target json files:

Nintendo Gamecube:

{
  "arch": "powerpc",
  "data-layout": "E-m:e-p:32:32-i64:64-n32",
  "dynamic-linking": false,
  "env": "newlib",
  "executables": true,
  "has-elf-tls": false,
  "has-rpath": true,
  "linker-flavor": "gcc",
  "llvm-target": "powerpc-eabi",
  "max-atomic-width": 32,
  "os": "dolphin",
  "target-c-int-width": "32",
  "target-endian": "big",
  "target-family": "unix",
  "target-mcount": "_mcount",
  "target-pointer-width": "32",
  "vendor": "nintendo"
}

Nintendo Wii:

{
  "arch": "powerpc",
  "data-layout": "E-m:e-p:32:32-i64:64-n32",
  "dynamic-linking": false,
  "env": "newlib",
  "executables": true,
  "has-elf-tls": false,
  "has-rpath": true,
  "linker-flavor": "gcc",
  "llvm-target": "powerpc-eabi",
  "max-atomic-width": 32,
  "os": "revolution",
  "target-c-int-width": "32",
  "target-endian": "big",
  "target-family": "unix",
  "target-mcount": "_mcount",
  "target-pointer-width": "32",
  "vendor": "nintendo"
}

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @JohnTitor (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[JohnTitor]

Looks good, let's re-run CI...

[JohnTitor]

It seems target_vendor is the newer change so we should gate it with the feature like const-extern-fn.

[DarkKirb]

I added another commit to gate the cfg checks behind a feature as well. It appears to work for a ppc linux target with version 1.13.0

[JohnTitor]

I think this would be better: JohnTitor@70e1129
This doesn't require the feature flag and it only applies cfg if Rust > 1.33.0.
You could tweak the condition and make sure rustc ci/style.rs && ./style src passes (I think it suggests using cfg_if! macros).

[DarkKirb]

it doesn't appear to do that, probably because i'm only using one layer of conditionals inside the cfg

also i added another commit that removes the addrinfo struct outright on devkitpro, because it's not defined anywhere in the header files never mind, the style check file doesn't accept two s! blocks in one file

[JohnTitor]

The changes look good to me. Does this work fine on your environment? If so, r=me once the commits are squashed.

[DarkKirb]

works fine on my end
r? @JohnTitor

[JohnTitor]

Hmm, it seems spurious:

+ cargo test --manifest-path libc-test/Cargo.toml --target aarch64-linux-android
   Compiling libc v0.2.74 (/checkout)
   Compiling libc-test v0.1.0 (/checkout/libc-test)
    Finished test [unoptimized + debuginfo] target(s) in 56.76s
     Running target/aarch64-linux-android/debug/deps/cmsg-8b6337b17e5d316d
/checkout/target/aarch64-linux-android/debug/deps/cmsg-8b6337b17e5d316d: 1 file pushed, 0 skipped. 10.8 MB/s (5735248 bytes in 0.505s)
status: exit code: 101
stdout ---

stderr ---
thread 'main' panicked at 'No option 'h' defined', /cargo/registry/src/git.colasdn.top-1ecc6299db9ec823/getopts-0.2.21/src/lib.rs:799:21
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

thread 'main' panicked at 'failed to find successful test run', /tmp/runtest.rs:45:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: test failed, to rerun pass '--test cmsg'

Re-triggering CI...

[JohnTitor]

Okay, finally it's green. Thanks for contributing!