Fix MSVC dependency issue between Clang-tablegen and LLVM-tablegen

Previously, when compiling Visual Studio targets, one could see random build errors. This was caused by tablegen projects using the same build folders.
This workaround simply chains tablegen projects.

Differential Revision: https://reviews.llvm.org/D54153


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349541 91177308-0d34-0410-b5e6-96231b3b80d8