ok - i have not tried but assume this does not compile on loongson -processor.
I don't have access to Longsoon or any other MIPS based architecture but I'd assume you'd have to do the same thing as for PPC compilations which is to disable all the x86 specific components (can't remember what they are off the top of my head). Your best bet is to set up a toolchain, grab the icecat source, and give it a try. Also, have a look at the Mozilla build documentation for library prerequisites
-Gary