The buildrump.sh script is a tool for (cross-)building rump kernels for a variety of platforms. The purpose is to make it easy to build rump kernels on any host for virtually any target. There are practically no dependencies apart from a (cross-)working toolchain. When invoked without parameters, buildrump.sh will download the necessary source code, build the kernel drivers for POSIX'y userspace, and run a number of tests.
See the wiki for more information and further instructions.