The kernel in the .cl file is also compiled by the native C++ cpu compiler, when using MiniCL.
When you want to debug the kernel using MiniCL, and want to put breakpoints, it is best to:
1) enabled the define #define DEBUG_MINICL_KERNELS 1 in Bullet/src/BulletMultiThreaded/MiniCL.cpp
2) temporarily remove the stringify lines in the .cl kernel, because it prevents the debugger from finding the right line.