Please allow to use the pre-install juce package instead of always bundling it

**Is your feature request related to a problem? Please describe.**
We would like to use the pre-built juce package.

**Describe the solution you'd like**
See the subject.

**Describe alternatives you've considered**
n/a

**Additional context**
This is for the FreeBSD port audio/giada. In the ports we always prefer to use packages instead of bundled versions.