core: sanitize RPATH in target tree before copying the overlay

core: sanitize RPATH in target tree before copying the overlay

We sanitize the RPATH of ELF files in the target tree to deal
with stupid packages that don't correctly use --prefix/DESTDIR
and that end up putting the full absolute build-time directory
in the RPATH.

We do it before copying the overlay and calling the post-build
script. The user is completely responsible for what happens
in the last two steps, and it should never be touched by us.

Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>