Make sure that debug dlls of OCC have different file names than from release build

[wwmayer]

With the latest LibPacks the debug and release dlls of OCC have the same file names. This makes it very difficult to make a debug build of FreeCAD to use the debug build of OCC.

OCC's CMake build scripts used to have an option where for the debug build the suffix "d" was added to the dlls.