Always build llvm with llvm
Always build llvm with llvm

this requires you to have a basic version of llvm in the path to bootstrap

Done because llvm trunk no longer compiles with gcc 4.6


Former-commit-id: 96360b6c45d669b03d72f04ec2dadb3812d6e057
darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide