==========
build_clang_rust - FAILED


***
*** Source code for the 'core' standard library could not be found
*** at '/usr/lib/rustlib/src/rust/library/core/src/lib.rs'.
***
***
*** Please see Documentation/rust/quick-start.rst for details
*** on how to set up the Rust support.
***
make[1]: *** [/srv/nipa-poller/net-next/wt-1/Makefile:1851: rustavailable] Error 1
make: *** [Makefile:248: __sub-make] Error 2