ddrescue: fix target build

ddrescue is not an autotools package. Convert to generic package to make
it build correctly for target architecture.

Cc: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>