I actually just answered my own question by reading the post
viewtopic.php?f=9&t=4238&p=15738&hilit=xcode#p15738I got the Xcode project to build by commenting out the appropriate lines in bullet-2.75/src/CMakeLists.txt before running cmake.
#if (CMAKE_SIZEOF_VOID_P MATCHES "8")
#SUBDIRS( BulletSoftBody BulletCollision BulletDynamics LinearMath )
#else (CMAKE_SIZEOF_VOID_P MATCHES "8")
SUBDIRS( BulletMultiThreaded BulletSoftBody BulletCollision BulletDynamics LinearMath )
#endif (CMAKE_SIZEOF_VOID_P MATCHES "8")
This fixed everything (as far as I can tell).
Thanks,
- D