When compiling EMC2 part of the RTAI headers includes asm/asm-offsets.h and this file is not found. In reality, there is a sym link, the asm directory, that was a dead link to asm-x86_64 which in the new kernel x86_64 was renamed to just x86.
cd /usr/src/linux-headers-2.6.24.x-realtime/include
ls -l -- confirm asm is a dead link
sudo rm asm
ln -s asm_x86 asm