Build rustlib/src together with prefix
Once https://static.redox-os.org/toolchain/$(TARGET)/relibc-install.tar.gz is rebuilt, it will be possible to remove the HUGE rust submodule as it is only needed by the small number of developers who work over the compiler and adapt the build system to this.
I tested this change on a clean build, both from binary prefix and from source.
Edited by uuuvn