CMake file exposure

[ScottCSteinhauser]

VHACD has been integrated into Facebook AI's habitat-sim, and the following changes were made to properly expose the VHACD apis as well as only build the neccessary files (These changes allow for the exclusion of src/test). Standard build within src/ still works.

[belalhmedan90]

v-hacd/src/test/src/main.cpp:120:43: error:

reference to ‘Material’ is ambiguous
  120 |     const unsigned int& nTriangles, const Material& material, IVHACD::IUserLogger& logger);

changing all Material names to Material_ in that file resolved the ambiguity.