autotools: modified autogen.sh to be able to build from different directory.
autotools: modified autogen.sh to be able to build from different directory.

Summary:
Right now we cannot have a designated build directory and we should build in the source directory. So the proposed solution lets you to build from any directory.

Signed-off-by: Srivardhan Hebbar <sri.hebbar@samsung.com>

Reviewers: raster, cedric

Differential Revision: https://phab.enlightenment.org/D1395

Signed-off-by: Cedric BAIL <240633aa59d25638de9800ef43a88ad2e208d24d@osg.samsung.com>

FlorentRevest/Elementary,tasn/elementary,rvandegrift/elementary,FlorentRevest/Elementary,rvandegrift/elementary,rvandegrift/elementary,tasn/elementary,tasn/elementary,FlorentRevest/Elementary,tasn/elementary,FlorentRevest/Elementary,tasn/elementary,rvandegrift/elementary