Travis config for a Rust project without `rustup.sh`

travis.yml

language: c
os:
  - linux
  - osx

matrix:
  - os: osx
    env: TARGET_TUPLE='x86_64-apple-darwin'
  - os: linux
    env: TARGET_TUPLE='x86_64-unknown-linux-gnu'

install:
  ## I don't have multi-os feature enabled yet...
  - "[ -z ${TARGET_TUPLE} ] && export TARGET_TUPLE='x86_64-unknown-linux-gnu'"
  - "export RUST_TARBALL=rust-nightly-${TARGET_TUPLE}.tar.gz"
  - "export CARGO_TARBALL=cargo-nightly-${TARGET_TUPLE}.tar.gz"
  - "curl -O --retry 3 http://static.rust-lang.org/dist/${RUST_TARBALL}"
  - "curl -O --retry 3 http://static.rust-lang.org/cargo-dist/${CARGO_TARBALL}"
  - "tar xf ${RUST_TARBALL}"
  - "tar xf ${CARGO_TARBALL}"

before_script:
    - "export LD_LIBRARY_PATH=${PWD}/rust-nightly-${TARGET_TUPLE}/lib"
    - "export PATH=${PWD}/rust-nightly-${TARGET_TUPLE}/bin:${PATH}"
    - "export PATH=${PWD}/cargo-nightly-${TARGET_TUPLE}/bin:${PATH}"
    - 'rustc --version'
    - 'cargo --version'

script:
  - cargo test