Trial and error has lead me to arm-linux-gnueabi-gcc
Is a more important question that I do not know how to answer. There should be a document some place?
Also I am defining the linker in ~/.cargo/config. It would be much better to define it on cargo's command line. Then it could live in my build scripts where it would be under version control. For me this wasted half day searching for the magic incantation to put in ~/.cargo/config started when my config file got accidentally deleted.