[llvm-lib] Add a dependency to intrinsics_gen to the LLVMLibDriver build

Summary:
Occasionally the build of LLVMLibDriver will fail because Attributes.inc has not been generated yet. Add an explicit dependency, so that we can guarantee that the file has been generated before LLVMLibDriver is build.

##[error]llvm\include\llvm\IR\Attributes.h(73,0): Error C1083: Cannot open include file: 'llvm/IR/Attributes.inc': No such file or directory
llvm\include\llvm/IR/Attributes.h(73): fatal error C1083: Cannot open include file: 'llvm/IR/Attributes.inc': No such file or directory [LLVMLibDriver.vcxproj]

Reviewers: asmith

Subscribers: mgorny, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64357

llvm-svn: 366097