The file of OrangePi_Doc.tar.bz2 was wrote by mistake, you could just ignore it and use the cross-compiler tool of Linux. Both Android and Linu share the same tool.
I tried to use mips-elf-gcc but compilation of modem source fails with unrecognized -march xcpu by mips-elf-gcc
Can some one please point to the pre-built mips-elf-gcc toolchain that was used to compile this source