NXO may crash basefirmware when linked against thumb version of libgcc depending on internal file offset

libgcc contains some thumb->ARM transitions in Codesourcery toolchain which are usually handled by arm-none-eabi-ld from binurils. As libgcc is compiled against ARMV4 targets it does not contain thumb-interworking code for ARMV5 architecture. The linker is expected to patch correct interworking code.

Last bugfix RCX-759 inserted correct interworking branches, but depending on the internal offset of the linked NXO an invalid BLX instruction may be created resulting in an undefined instruction exception.