fix(build-project): accidentally overwriting options

[DavidVujic]

Description

The build-project command unintentionally had overwritten the poetry build command options.

Also, a typo in how the new with-top-namespace option was picked up.

Motivation and Context

Fixes #28

How Has This Been Tested?

Installed a new version with the code in this Pull Request.

Ran build-project with, and without, the -f flag, in combination with the with-top-namespace flag.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• I have read the code of conduct.
• I have read the contributing guide.
• I have updated the documentation accordingly (if applicable).