I've recently done a source update of rustc, and have been greeted by an error like "No rule to make target src/liballoc_jemalloc/../jemalloc/include/jemalloc/internal/ph.h, needed by src/jemalloc.o".
I could work around the issue by removing the build/x86_64-unknown-linux-gnu/native/jemalloc/ directory and rebuilding, but its a build system issue if that is not done for me, or if the makefile is not regenerated.