[msvc] Fix quoting of OSRM_PROJECT_DIR as preprocessor define
[msvc] Fix quoting of OSRM_PROJECT_DIR as preprocessor define

It looks MSVC still special handling, no quotoing as well as
additional quoting like add_definitions(-DFOO="\\"foo\\"")
as per https://cmake.org/pipermail/cmake/2007-June/014611.html
does not seem to handle CMake variables correctly.

This Visual C++ specific fix is based on this solution
https://cmake.org/pipermail/cmake/2006-September/011292.html

frodrigo/osrm-backend,yuryleb/osrm-backend,bjtaylor1/osrm-backend,bjtaylor1/osrm-backend,oxidase/osrm-backend,Project-OSRM/osrm-backend,yuryleb/osrm-backend,Project-OSRM/osrm-backend,oxidase/osrm-backend,yuryleb/osrm-backend,Project-OSRM/osrm-backend,frodrigo/osrm-backend,oxidase/osrm-backend,oxidase/osrm-backend,felixguendling/osrm-backend,felixguendling/osrm-backend,bjtaylor1/osrm-backend,yuryleb/osrm-backend,felixguendling/osrm-backend,frodrigo/osrm-backend,Project-OSRM/osrm-backend,frodrigo/osrm-backend,bjtaylor1/osrm-backend