Improve support for NMake-based builds
To build CAMPVis using NMake one had to manually copy several external DLLs into the CMake output directory. There were 2 reasons for that: - our macros treated NMake as a compiler and didn't try to detect what compiler NMake will actually use; as a result, they couldn't find the right external DLLs for NMake-based builds - Visual Studio manages build types independently of CMake and always outputs into a build-type-specific sub-directory of the CMake output directory — that's where we place external DLLs; NMake, on the other hand, relies on CMake for build type selection and will output directly into the CMake output directory; due to this discrepancy, NMake-based builds couldn't find the external DLLs that were copied into the build directory As many popular IDEs (e.g. Qt Creator, Code::Blocks, Eclipse CDT) rely on NMake to build projects on Windows, it makes sense to have a working support for NMake in our build system. Update our compiler detection macros and adjust the CMake output directory to match that of Visual Studio when NMake is used to improve the support for NMake-based builds.