Allow specifying target project.xml in target configuration or task configuration.

[EliteMasterEric]

Currently, the project file is specified in lime.projectFile and thus only one project can be accessed by Lime build tasks at a time. Adding this as an option which is configurable on a per-task or per-configuration basis would resolve this.

Use case: I am developing with PolyMod, which has a sample folder that contains four example projects. I would like to be able to use the Run configuration dropdown to select between each of these, but each has its own project file and the current setup does not allow this.

[47rooks]

I think this would be really useful. I have a multi-root project where I have project.xml files in two different directories - examples and tests, and I want to be able to switch between them easily.

[ACrazyTown]

I'm also interested in this