clean llvm resource in compiler (libgbe.so)

clean llvm resource in compiler (libgbe.so)

since we have separated the compiler (libgbe.so) and the interpreter
(libgbeinterp.so), the LLVM resource cleanup task should be done in
the compiler instead of the GenProgram::~GenProgram which has no way
to clean llvm resources in libgbeinterp.so

Signed-off-by: Guo Yejun <yejun.guo@intel.com>
Reviewed-by: "Luo, Xionghu" <xionghu.luo@intel.com>