undefined symbol: ompt_start_tool

Has anyone encounter the following error? I am wondering if it is something to do with how I build libomp.so.

$ LD_LIBRARY_PATH=/home/kli/clang-install/lib mpirun -np 1 ./a.out
a.out: symbol lookup error: /home/kli/clang-install/lib/libomp.so: undefined symbol: ompt_start_tool