something like:

```
- when: platform == 'Darwin'
  name: no_unused_but_set_variable
  files: [no_unused_but_set_variable.patch]
  before: configure
  handler: bash
  bash: |
    if [[ "$MACOSX_DEPLOYMENT_TARGET" = "10.7" ]]; then 
    patch -p1 < _hashdist/no_unused_but_set_variable.patch
   fi
```