It's the nonstandard location that is the problem, really. The --extra-lib-dirs thing should have caused the special location to be used, but it relies on whoever wrote the bindings paying attention to extra-lib-dirs.

On Linux, you have /etc/ld.so.conf as a list of directories to search for shared objects and LD_LIBRARY_PATH to add extra directories to it. On OS X, shared library paths are normally compiled into the things that use them and DYLD_LIBRARY_PATH overrides this completely (which means setting it can cause all programs to fail to find any shared libraries, oops!). DYLD_FALLBACK_LIBRARY_PATH is tried if it can't find the shared library at its normal location, which is risky but safer than DYLD_LIBRARY_PATH.

If that shared object /Users/batman/Library/Haskell/ghc-7.8.3-x86_64/lib/mysql-0.1.1.7/libHSmysql-0.1.1.7-ghc7.8.3.dylib was built with the right option (-headerpad_max_install_names, IIRC) then you may be able to use install_name_tool to fix the shared object path in it. You'll need to use otool -L to check what name is there and then install_name_tool to replace it.

Alternately you can check with otool -L what pathname was stored in the mysql shared library itself and maybe fix that with install_name_tool.