compile clang issue


I encounter a issue about compile and install clang/llvm tools.

After compile many time about clang, I locate the problem

Llvm can be successful compile and install so as the clang tools.

When complile compliler-rt in the location /llvm/projects/complier-rt, I encounter the problems as fellows:

make/ *** ‘make/platform/’: must define one of ‘UniversalArchs’ and ‘Arch’. Stop

I can’t find a way to solve this issue? Could you help me to solve this problem.