envsetup: Show error when supplied dir isn't present with mmm

When a directory isn't present with mmm, don't show "No Android.mk present", rather show that the directory isn't present

Change-Id: I7259a60012c6f30c470daa60d5a5097d01ffc4c7
Signed-off-by: Abhinav1997 <abhinav.jhanwar.august2@gmail.com>