Check for local wheel updates when re-locking

[neilmehta24]

I have run into a problem with the following workflow:

• Create local wheel with a unique version, and update the lock file
• Regenerate the local wheel as the same version, but different hash
• Re-lock the layers and build

The build fails with a hash mismatch error, because the hash of the local wheel was not updated during the re-lock after the regeneration. This issue is related to #22 . The workaround is to delete the requirements files before re-locking