package/efl/libelementary: disable on static lib only build

libelementary sources include dlfcn.h header when HAVE_FORK symbol is defined;
this is always the case because efl already depends on BR2_USE_MMU.

Fixes:
  http://autobuild.buildroot.org/results/07c/07c97918dab24215f5c5130a9cd2788adca0a27d/



Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>