title: failure to build rust-libc using cargo when rustc is musl-enabled
body: <p>I successfully created a <code>musl</code> configured <code>rustc</code> by following <a href="https://github.com/rust-lang/rust/blob/master/src/doc/trpl/advanced-linking.md" rel="nofollow">this link</a></p>
  
  <p>My attempt to build a project (which builds fine using non-musl configured rust) failed when I used <code>cargo rustc -- --target=x86_64-unknown-linux-musl</code></p>
  
  <pre><code> 'error: could not find crate `libc` with expected target triple x86_64-unknown-linux-musl'
  </code></pre>
  
  <p>Then, I tried to create <code>rust-libc</code> library using the code from crate. To be more accurate, I used the command provided by <code>cargo</code> to build <code>rust-libc</code>, I've only added <code>--target=x86_64-unknown-linux-musl</code> to the command.  This time it failed reporting:</p>
  
  <pre><code>'error: could not find native static library `c`, perhaps an -L flag is missing?`'
  </code></pre>
  
  <p>I have two questions:</p>
  
  <ul>
  <li><p>Is it mandatory to build <code>musl</code> configured <code>cargo</code> to be able to use <code>cargo build --target=x86_64-unknown-linux-musl</code>?</p></li>
  <li><p>How can I address this:</p>
  
  <pre><code>'error: could not find native static library `c`, perhaps an -L flag is missing?'
  </code></pre></li>
  </ul>