rust/.azure-pipelines/steps/install-clang.yml

steps:

- bash: |
    set -e
    curl -f http://releases.llvm.org/7.0.0/clang+llvm-7.0.0-x86_64-apple-darwin.tar.xz | tar xJf -

    export CC=`pwd`/clang+llvm-7.0.0-x86_64-apple-darwin/bin/clang
    echo "##vso[task.setvariable variable=CC]$CC"

    export CXX=`pwd`/clang+llvm-7.0.0-x86_64-apple-darwin/bin/clang++
    echo "##vso[task.setvariable variable=CXX]$CXX"

    # Configure `AR` specifically so rustbuild doesn't try to infer it as
    # `clang-ar` by accident.
    echo "##vso[task.setvariable variable=AR]ar"
  displayName: Install clang (OSX)
  condition: and(succeeded(), eq(variables['Agent.OS'], 'Darwin'))

# If we're compiling for MSVC then we, like most other distribution builders,
# switch to clang as the compiler. This'll allow us eventually to enable LTO
# amongst LLVM and rustc. Note that we only do this on MSVC as I don't think
# clang has an output mode compatible with MinGW that we need. If it does we
# should switch to clang for MinGW as well!
#
# Note that the LLVM installer is an NSIS installer
#
# Original downloaded here came from
# http://releases.llvm.org/7.0.0/LLVM-7.0.0-win64.exe
# That installer was run through `wine` on Linux and then the resulting
# installation directory (found in `$HOME/.wine/drive_c/Program Files/LLVM`) was
# packaged up into a tarball. We've had issues otherwise that the installer will
# randomly hang, provide not a lot of useful information, pollute global state,
# etc. In general the tarball is just more confined and easier to deal with when
# working with various CI environments.
- bash: |
    set -e
    mkdir -p citools
    cd citools
    curl -f https://rust-lang-ci2.s3.amazonaws.com/rust-ci-mirror/LLVM-7.0.0-win64.tar.gz | tar xzf -
    echo "##vso[task.setvariable variable=RUST_CONFIGURE_ARGS]$RUST_CONFIGURE_ARGS --set llvm.clang-cl=`pwd`/clang-rust/bin/clang-cl.exe"
  condition: and(succeeded(), eq(variables['Agent.OS'], 'Windows_NT'), eq(variables['MINGW_URL'],''))
  displayName: Install clang (Windows)

# Note that we don't install clang on Linux since its compiler story is just so
# different. Each container has its own toolchain configured appropriately
# already.