Improve ICE message when data-layouts don't match
Improve ICE message when data-layouts don't match

LLVM target name does not necessarily match the Rust target name and it
can be confusing when the ICE message is describing a target other than
has been specified on the command line.

aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust