`LLVM_ENABLE_MODULES` builds sometimes fail because `Intrinsics.td`
needs to regenerate `Instrinsics.h` before anyone can include anything
from the LLVM_IR module. Represent the dependency explicitly to prevent
that.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239796 91177308-0d34-0410-b5e6-96231b3b80d8