PBQP register allocator not supported for X86

I am building LLVM 10.0.1 from source for X86 target, the build completed successfully but when I am compiling using clang(build from source) with “regalloc” flag set to “pbqp”, following error is thrown

clang (LLVM option parsing): for the --regalloc option: Cannot find option named 'pbqp'!

My question is how can I use pbqp register allocator with clang(build from source) for X86 target?