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

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

Summary:
Right now we cannot have a designated build directory and build in the same folder as in the source. So modified the autogen.sh so that we can have a designated build directory and can build from that.

@feature

Signed-off-by: Srivardhan Hebbar <sri.hebbar@samsung.com>
Reviewers: cedric, raster, devilhorns

Subscribers: zmike, cedric

Differential Revision: https://phab.enlightenment.org/D1359

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