this reverts 5c04730534ea7933855429c5fc5dc7b22eba7bc2.

sadly the quality of the intel dialect in llvm's assembly
parser has many frustrating bugs, and generally has unfortunate
syntax.

the plan is to use AT&T for now since it at least works,
and eventually zig will have its own assembly parser for
x86 and it will be as close to NASM as possible.