make-linux: add an rpath for shared libraries
make-linux: add an rpath for shared libraries

If our output depends on a .so, add a binary-relative rpath to the library
directory to our link line.  This allows us to run binaries without
LD_LIBRARY_PATH.

Review URL: http://codereview.chromium.org/7528008

csulmone/gyp,csulmone/gyp,csulmone/gyp,csulmone/gyp