Testing OMPD: fix testing, add testing instructions

[jprotze]

make check-ompd VERBOSE=1

cd ..../BUILD/libompd/test && lit ..../BUILD/libompd/test -avv

bash -c "(clang --verbose -fopenmp -g .../SRC/libompd/test/openmp_examples/example_1.c \
-o .../BUILD/libompd/test/openmp_examples/Output/example_1.c.tmp  \
-I /home/pj416018/OMPD/openmp-rt-ompd/libompd/test -I .../BUILD/runtime/src && \
env OMP_DEBUG=enabled gdb -x .../BUILD/libompd/test/../gdb-plugin/__init__.py\
 -x .../SRC/libompd/test/test.cmd \
.../BUILD/libompd/test/openmp_examples/Output/example_1.c.tmp) |&\
 FileCheck .../SRC/libompd/test/openmp_examples/example_1.c"

currently the tests siliently succeed, because the |& fetches the error code from compiling