Patch borrowed from OpenEmbedded, available at
recipes/libaio/libaio-0.3.106/destdir.patch in their source tree.

It just adds support for the traditional DESTDIR variable to install
the library in a different sysroot than the normal /.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
[JEM: I couldn't verify the initial author of this change, but it's
 trivial.  For information on the DESTDIR convention, see:
 https://www.gnu.org/prep/standards/html_node/DESTDIR.html

]
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>