Final Cut X will not run on an AMD System cause of missing SSSE3 instructions.
Use final cut pro 7 which will work.

Did you boot into 64 bit mode?
You can try to disable on the fly patching cause some apps will not work without compressing it with upx.
Just use the flag std_dyld=Yes and patch your dyld binaries.

I never had problems compiling x86_64 binaries.