Well you need to have a recent version (here: 5.0) of kdevplatform installed. kdevplatform (shell, language agnostic infrastructure, vcs plugins, etc. pp.) is a set of libraries KDevelop is based on.
Get kdevplatform from:
git://anongit.kde.org/kdevplatform
Install kdevplatform, kdevelop, kdev-rust, etc. into the same install prefix (-DCMAKE_INSTALL_PREFIX=/foo) and you should be fine.