Prefer local binaries when running execa

[Helehelehele]

Change description

This change makes execa use the local compodoc binary.

Type of change

• Bug fix (fixes an issue)
• New feature (adds functionality)

Related issues

Fixes #15
JIRA: ZCLI-47

Checklists

Development

• Lint rules pass locally
• Application changes have been tested thoroughly
• Automated tests covering modified code pass

Security

• Security impact of change has been considered
• Code follows company security practices and guidelines

Code review

• Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached as necessary
• "Ready for review" label attached and reviewers assigned
• Changes have been reviewed by at least one other contributor
• Pull request linked to task tracker where applicable