Avoid duplicate Makefile targets for gyp exectuble targets.
Avoid duplicate Makefile targets for gyp exectuble targets.

executables usually have the same alias name as the gyp target name, so don't
add a make target for the alias name when it was already added for the gyp
target name.
Review URL: http://codereview.chromium.org/1321001

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