icecc.bbclass: Skip canadian-cross compiles

icecc.bbclass will no longer attempt to distribute cross-canadian
compiles. While it is technically possible to generate a toolchain that runs
on the build system and generates executables for the host system, this
is not the normal way that icecc operates. There are so few of these
recipes that it is probably not worth maintaining a distinct code path
for them.

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>