[CMake] Bug 23468 - LLVM_OPTIMIZED_TABLEGEN does not work with Visual Studio

Summary: Multi-configuration builds put their binaries into ${CMAKE_BINARY_DIR}/Release/bin/. The table-gen cross-compilation support needs to take that into account.

Reviewers: yaron.keren

Reviewed By: yaron.keren

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10102

llvm-svn: 238592