Travis CI Mac and MIPS builds fail for unmodified master

[jimblandy]

In pull request #128, the Travis CI builds failed in a way that didn't seem to have anything to do with my patch, so I reverted my changes and re-pushed with a tree identical to master. The same builds failed in the same way.

According to the build results, the Mac ARCH=x86_64 build fails with the following message:

/Users/travis/.cargo/registry/src/github.com-88ac128001ac3a9a/bitflags-0.3.3/src/lib.rs:1:1: 1:1 error: the crate std has been compiled with rustc 1.7.0-nightly (d4b67cd7c 2016-01-01), which is incompatible with this version of rustc [E0514]

The Mac ARCH=i686 build fails with the message:

src/lib.rs:1:1: 1:1 error: the crate std has been compiled with rustc 1.7.0-nightly (d4b67cd7c 2016-01-01), which is incompatible with this version of rustc [E0514]

and the TARGET=mips-unknown-linux-gnu build fails with the messages:

/usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Dwarf Error: found dwarf version '4', this reader only handles version 2 and 3 information.
/usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Dwarf Error: found dwarf version '0', this reader only handles version 2 and 3 information.
/home/travis/rust/lib/rustlib/mips-unknown-linux-gnu/lib/liballoc_jemalloc-17a8ccbd.rlib(jemalloc.pic.o): In function malloc_conf_init': /buildslave/rust-buildbot/slave/nightly-dist-rustc-cross-linux/build/src/jemalloc/src/jemalloc.c:(.text.malloc_conf_init+0x94): undefined reference tosecure_getenv'
/usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Dwarf Error: found dwarf version '0', this reader only handles version 2 and 3 information.
/usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Dwarf Error: found dwarf version '3072', this reader only handles version 2 and 3 information.
/buildslave/rust-buildbot/slave/nightly-dist-rustc-cross-linux/build/src/jemalloc/src/jemalloc.c:(.text.malloc_conf_init+0x98): undefined reference to `secure_getenv'
collect2: ld returned 1 exit status

after many warnings similar to:

/usr/lib/gcc/mips-linux-gnu/4.4.5/../../../../mips-linux-gnu/bin/ld: Warning: /home/travis/build/rust-lang-nursery/libc/libc-test/target/mips-unknown-linux-gnu/debug/libc_test uses hard float, /home/travis/rust/lib/rustlib/mips-unknown-linux-gnu/lib/libcompiler-rt.a(mulodi4.o) uses soft float

[alexcrichton]

Indeed! This'll be fixed by #114 and is basically a dupe of #100, so I'm gonna close in favor of that. Should be handled soon though!