title: Specific profiles for workspace members
body: <p>Is it possible to specify specific profiles for members of a workspace?
  If I write a profile into the member <code>Cargo.toml</code> I get:</p>
  
  <blockquote>
    <p>warning: profiles for the non root package will be ignored, specify profiles at the workspace root:</p>
  </blockquote>
  
  <p>I also tried to put a specific profile into workspace root's <code>Cargo.toml</code>:</p>
  
  <pre><code>[profile.release]
  opt-level = 3
  
  [profile.release.hal]
  # optimizer kills assembly code
  opt-level = 1
  </code></pre>
  
  <p>However, it seems to be ignored too, as the applied options in the the verbose output show:</p>
  
  <blockquote>
    <p>Running `rustc --crate-name hal src/hal/lib.rs --crate-type lib -C opt-level=3 --emit=dep-info,link [...]</p>
  </blockquote>
  
  <p>Is there any other way beside avoiding workspaces at all?</p>