You could try further editing user.settings to force it to use the icc compiler instead of calling g++. Basically, look for the type of compiling you want in the basic.settings file, and fill those in as override options in user.settings.
It might also be that icc still isn’t on the path scons expects for some reason?
We’ve also had issues in the past with “unsupported” versions of icc and gcc – basically there’s a list of versions in basic.settings somewhere like [3.0, 3.1, 3.2, 4.0, 4.1, …] and you can just add your version to that list to get it to work. (Of course untested compilers may throw compilation errors.) I don’t think this is your problem.