entd: add libdl for dlopen and friends

This is needed by libcrosapi.  A cleaner fix would be to add a pkgconfig to libcrosapi, which
entd would use to determine its dependencies, but this is much more expedient.

Change-Id: Idfedcd3c3025a64e836b3e65e8c3d9bfb24998ee

BUG=None
TEST=re-make entd in chroot, verify that -ldl appears in linker command line

Review URL: http://codereview.chromium.org/3575015
1 file changed