title: rust compile x86 library on x86_64 machine
body: <p>I have ubuntu x86_64 container and <code>cargo build</code> goes well.
  But i need to build x86 library version too.
  As far as I understand i need to add i686 toolchain and target.</p>
  
  <pre><code>rustup target add i686-unknown-linux-gnu done successful
  </code></pre>
  
  
  
  <pre><code>rustup toolchain install stable-i686-unknown-linux-gnu finished with error
  </code></pre>
  
  
  
  <pre><code>$ rustup toolchain install stable-i686-unknown-linux-gnu
  info: syncing channel updates for 'stable-i686-unknown-linux-gnu'
  info: latest update on 2018-11-08, rust version 1.30.1 (1433507eb 2018-11-07)
  info: downloading component 'rustc'
  info: downloading component 'rust-std'
  info: downloading component 'cargo'
  info: downloading component 'rust-docs'
  info: installing component 'rustc'
  info: installing component 'rust-std'
  info: installing component 'cargo'
  info: installing component 'rust-docs'
  
    stable-i686-unknown-linux-gnu installed - (error reading rustc version)
  </code></pre>
  
  <p>and</p>
  
  <pre><code>$ rustup  default stable-i686
  info: using existing install for 'stable-i686-unknown-linux-gnu'
  info: default toolchain set to 'stable-i686-unknown-linux-gnu'
  
    stable-i686-unknown-linux-gnu unchanged - (error reading rustc version)
  </code></pre>
  
  <p>Do I missed something or took wrong approach? </p>