[CMake] Default options for faster executables on MSVC

- Disable incremental linking by default. /INCREMENTAL adds extra thunks in the EXE, which makes execution slower.
- Set /MT (static CRT lib) by default instead of CMake's default /MD (dll CRT lib). The previous default /MD makes all DLL functions to be thunked, thus making execution slower (memcmp, memset, etc.)
- Adds LLVM_ENABLE_INCREMENTAL_LINK which is set to OFF by default.

Differential revision: https://reviews.llvm.org/D55056


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349517 91177308-0d34-0410-b5e6-96231b3b80d8