i128 intrinsics
Adds i128 intrinsics.
Note that this PR doesn't do float intrinsics, due to the missing presence of macros, those are however still required in order for rustc to switch to this crate.
Two reasons:
* the C versions __divti3 and __modti3 are apparently broken,
at least when used in quickcheck. They change their own arguments.
* compiler_rt's support for mips is disabled already on clang [1].
Its desireable to support working "cargo test" on that compiler
as well, and not greet the tester with linker errors.
[1]: http://llvm.org/viewvc/llvm-project?view=revision&revision=224488
- add #[no_mangle] to the panic_fmt lang item to adjust to changes in
the visibility algorithm
- adjust to changes in the layout of Cargo's target directory
- use a newer Xargo to reduce the build time of the sysroot (only core
is compiled as part of the sysroot now)
this version uses the rust-src component that rustup installs instead
of fetching the source tarball from static.r-l.o, which sometimes went
wrong due to the fallible logic that Xargo 0.1.x used
`apt update` and `apt install` should be in the same Docker RUN statement, otherwise `apt update` will be cached and `apt install` will 404 if a package no longer exists.
mention that 'extern crate compiler_builtins' must be used
in some crate that's part of the dependency graph of the crate one's
building.
r? @alexcrichton
test the mips64 targets
These should be all the required changes I think but libloading can't be cross compiled for these new targets:
```
error: failed to run custom build command for `libloading v0.3.1`
process didn't exit successfully: `/target/debug/build/libloading-07147fe7fffab0b2/build-script-build`(exit code: 101)
--- stderr
thread 'main' panicked at 'could not get target info: TargetNotFound', ../src/libcore/result.rs:799
note: Run with `RUST_BACKTRACE=1` for a backtrace.
```
I've openend nagisa/rust_libloading#19 to track that. Wel'll have to wait until that's fixed.
cc @alexcrichton
