rust: add initial changes to support powerpc64le musl

[mksully22]

Initial changes to support rustc building on ppc64le with musl. A PR was also submitted to libc component rust-lang/libc#1023 to add changes to libc musl definitions.

A PR was submitted on Alpine alpinelinux/aports#4549 with equivalent temporary patches for building on Alpine for now.

As a verification test a github project was put together to build ppc64le versions of rustc, rust-stdlib, and cargo on Alpine, https://github.com/mksully22/ppc64le_alpine_rust_1.26.2

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @varkor (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 Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed.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.

[rust-highfive]

The job x86_64-gnu-llvm-3.9 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:05:53]    Compiling parking_lot_core v0.2.14
[00:05:54]    Compiling tempdir v0.3.7
[00:05:56]    Compiling rls-span v0.4.0
[00:05:56]    Compiling chalk-engine v0.6.0
[00:05:57] error[E0432]: unresolved import `LinkerFlavor`
[00:05:57]   --> librustc_target/spec/powerpc64le_unknown_linux_musl.rs:11:5
[00:05:57] 11 | use LinkerFlavor;
[00:05:57] 11 | use LinkerFlavor;
[00:05:57]    |     ^^^^^^^^^^^^ no `LinkerFlavor` in the root
[00:05:57] 
[00:05:57] error[E0432]: unresolved import `target`
[00:05:57]   --> librustc_target/spec/powerpc64le_unknown_linux_musl.rs:12:5
[00:05:57]    |
[00:05:57] 12 | use target::{Target, TargetResult};
[00:05:57]    |     ^^^^^^ Maybe a missing `extern crate target;`?
[00:05:57]    Compiling rustc_apfloat v0.0.0 (file:///checkout/src/librustc_apfloat)
[00:05:59] error: aborting due to 2 previous errors
[00:05:59] 
[00:05:59] For more information about this error, try `rustc --explain E0432`.
[00:05:59] For more information about this error, try `rustc --explain E0432`.
[00:05:59] error: Could not compile `rustc_target`.
[00:05:59] 
[00:05:59] Caused by:
[00:05:59]   process didn't exit successfully: `/checkout/obj/build/bootstrap/debug/rustc --crate-name rustc_target librustc_target/lib.rs --color always --error-format json --crate-type dylib --emit=dep-info,link -C prefer-dynamic -C opt-level=2 --cfg feature="jemalloc" -C metadata=58741ed9de9aae4f -C extra-filename=-58741ed9de9aae4f --out-dir /checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/deps --target x86_64-unknown-linux-gnu -L dependency=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/deps -L dependency=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/release/deps --extern serialize=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/deps/libserialize-5d0a8a65bb9fe29f.so --extern serialize=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/deps/libserialize-5d0a8a65bb9fe29f.rlib --extern bitflags=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/deps/libbitflags-99b4534960f92449.rlib --extern rustc_cratesio_shim=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/deps/librustc_cratesio_shim-056d8bc457dc18d8.so --extern log=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/deps/liblog-5073f1296cd24b67.rlib` (exit code: 101)
[00:06:01] error: build failed
[00:06:01] error: build failed
[00:06:01] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "build" "--target" "x86_64-unknown-linux-gnu" "-j" "4" "--release" "--locked" "--color" "always" "--features" " jemalloc" "--manifest-path" "/checkout/src/rustc/Cargo.toml" "--message-format" "json"
[00:06:01] expected success, got: exit code: 101
[00:06:01] thread 'main' panicked at 'cargo must succeed', bootstrap/compile.rs:1091:9
[00:06:01] travis_fold:end:stage0-rustc

[00:06:01] travis_time:end:stage0-rustc:start=1529340107408390867,finish=1529340145361063440,duration=37952672573


[00:06:01] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap build
[00:06:01] Build completed unsuccessfully in 0:00:52
[00:06:01] make: *** [all] Error 1
[00:06:01] Makefile:28: recipe for target 'all' failed

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:10a7f28c
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
---
travis_time:end:0cd65d2e:start=1529340145906491205,finish=1529340145912011310,duration=5520105
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:169a69a4
$ head -30 ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
head: cannot open ‘./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers’ for reading: No such file or directory
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:034ad096
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[varkor]

Nit: Copyright 2018.

[varkor]

Thanks! This looks right to me, but I'm unfamiliar with this part of the codebase, so I'm going to assign someone else to double-check.

r? @Mark-Simulacrum

[Mark-Simulacrum]

r? @eddyb

I'm not sure what the policy is currently for adding new targets into the compiler itself. Maybe we should FCP.

[eddyb]

r? @alexcrichton or @nagisa

[alexcrichton]

r=me with the year fix, thanks @mksully22!

[TimNN]

Ping from triage, @mksully22: This PR requires a minor fix from you.

[malbarbo]

The author did the fix.

[alexcrichton]

@bors: r+

[bors]

📌 Commit dd069ea has been approved by alexcrichton

[pietroalbini]

@bors rollup

[gnzlbg]

cc @lu-zero

[lu-zero]

I do not have a musl chroot handy to compile it myself right now, but from a cursory look looks fine.