You're on the right track. The first thing to do is try compiling it without the JIT. Remove definitions for
-D FEATURE_NANOJIT -D JS_TRACER -D AVMPLUS_IA32=1 -D AVMPLUS_LINUX=1
If you can get jsdb.cpp to compile under those conditions, then you can edit jsdb.project and add a new platform ("raspberry"). Copy the linux <platform> definition and modify the compiler flags as appropriate for your cross-compiler.
In the "release" and "debug" modes, update these lines so they will be used in every platform except raspberry.
JSDB builds itself. The compile scripts (makejsdb.*) are generated with ...
./jsdb make.js jsdb.project raspberry /preview > makeraspberry.csh; chmod +x makeraspberry.csh
If you get that working, you can save time in compiling by letting JSDB manage the compilation process
./jsdb make.js jsdb.project raspberry
Be sure your binary output file doesn't overwrite jsdb on your host!