Is it OK to add it as environment variable?
This should work:
export LIBRARY_PATH=$LIBRARY_PATH:/usr/local/lib
Notice, it's LIBRARY_PATH
, not LD_LIBRARY_PATH
.
On the other hand, if that doesn't work for you, you should compile with the flag:
-L/usr/local/lib
And that should be sufficient, too.
EDIT: Btw, I don't know why you're using back-slashes instead of slashes... that needs explanation. Use slashes always. Even on Windows.