Update server to launch without magma plugin

[kmpepper]

Description

• follow up to decoupling caldera core with magma plugin dependencies, updating server.py to still launch with --build flag even when magma plugin is not present

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• unit tests
• server run with --build flag & no magma dir, with --uidev flag and no magma

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud