custom bullet header path and library names
Please allow for a custom bullet header path and library names
In gentoo the headers are under /usr/include/bullet/
(e.g.: /usr/include/bullet/BulletCollision/CollisionShapes/btCollisionShape.h
) and the libraries are named libBulletCollision.so
last there isn't a libbulletmath.so
or libBulletMath.so