3rdparty : add support for Jamfile.haiku for independent 3rdparty source code
|Reported by:||mmadia||Owned by:||bonefish|
Imagine Application_A currently has its own set of Jamfiles. It also has a Jamfile.haiku, which is only used when Application_A is located in haiku/3rdparty
This is to help developers integrate independent applications into Haiku's build system more easily, without removing the ability to be built outside of the tree.