[scons] arm: disable gneration of listing
[scons] arm: disable gneration of listing

This saves about 1GB of disk space for
a xpcc test build.

dergraaf/xpcc,chrism333/xpcc,dergraaf/xpcc,chrism333/xpcc,chrism333/xpcc,dergraaf/xpcc,chrism333/xpcc,dergraaf/xpcc