I have llvm installed, although possibly relevant on Ubuntu it has installed lld as lld-10. I have symlinked /usr/bin/lld -> usr/bin/lld-10 just to make sure.
ld exists in /usr/bin/ld
However when I try to cargo build I get the error:
You choose linkers not by overriding the ld command but choosing to run ld.bfd, ld.gold, ld.lld, etc.
It's the bit after the dot in ld.xyz that you specify in -fuse-ld=xyz. So just make sure that /usr/bin/ld.lld points to your linker and should be good. Something like