package.bbclass: Fix handling of symlinks in debug packages

package.bbclass: Fix handling of symlinks in debug packages

When copying the sources for the debug source package we use cpio -Ll
which means to copy files as hardlinks and to dereference symlinks.
It appears there is a bug in cpio since -Ll will copy symlinks and
not dereference them. We therefore do a second pass over copied symlinks
resolving them into files. Ideally we would copy these as hardlinks as well
however it doesn't seem worth the extra code and effort for what amounts
to a corner case for a minor space improvement.

This means that the -dbg packages no longer contain broken symlinks.

[YOCTO #5020]

(From OE-Core rev: 2ca2c4747f645a0d478c2171fff4c65752188285)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>