Ah ok, in that case you might want to try building it on the device if you have gcc installed on it. That will take a while and you may have to create a swapfile but that's the easiest way (there was someone on reddit who seems to have gotten it to work on a raspberry pi that way without changing anything).
Otherwise if I recall correctly, you can use a CC and CXX argument when calling scons to point to your crosscompiler ... but since it's been a while since I last did that I can't remember if I also had to change something in the SConstruct file for it to work properly ...
(Looking at the current SConstruct it seems to offer CC CXX CFLAGS CCFLAGS and LINKFLAGS)