ci: Add Android llama demo app build check

[chmjkb]

Description

Adds Llama demo app build for Android to the CI. Also makes some performance improvements by prevending duplicate build runs within the same branch.

Type of change

• 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)
• Documentation update (improves or adds clarity to existing documentation)

Tested on

• iOS
• Android

Testing instructions

Screenshots

Related issues

Checklist

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly
• My changes generate no new warnings

Additional notes