Fix CK_BAD propagation for --odr

Fix CK_BAD propagation for --odr

With the reproducer from PR26252 we get:
...
$ dwz 2 -o 2.z --odr -lnone
dwz: dwz.c:7396: partition_found_dups: \
  Assertion `die->die_ck_state == CK_KNOWN' failed.
Aborted (core dumped)
...

The problem is caused by the odr code in checksum_ref_die, which skips
checksum calculation for the children of odr types, with as unintended
side-effect that it break the CK_BAD propagation to toplevel DIEs.

Fix this by making the skipping of the checksum calculation less intrusive.
Specially:
- undo all modifications related to odr in checksum_ref_die
- After calling checksum_ref_die in read_debug_info:
  - override die_ref_hash for odr DIEs, and
  - recalculate die_ref_hash for all other DIEs.

We still have the same amount of compression with cc1, that is: without odr
we have 42.30% reduction:
...
$ dwz cc1 -o cc1.z -lnone --no-odr
$ diff.sh cc1 cc1.z
.debug_info      red: 44.84%    111527248  61527733
.debug_abbrev    red: 40.28%    1722726  1028968
.debug_str       red: 0%        6609355  6609355
total            red: 42.30%    119859329 69166056
...
and with odr but without the bug fix we have 54.55%:
...
$ dwz cc1 -o cc1.z -lnone --odr
$ diff.sh cc1 cc1.z
.debug_info      red: 57.46%    111527248  47449258
.debug_abbrev    red: 75.08%    1722726  429434
.debug_str       red: 0%        6609355  6609355
total            red: 54.55%    119859329 54488047
...
and with odr and the bug fix still 54.55%:
...
$ dwz cc1 -o cc1.z -lnone --odr
$ diff.sh cc1 cc1.z
.debug_info      red: 57.46%    111527248  47446501
.debug_abbrev    red: 75.51%    1722726  422027
.debug_str       red: 0%        6609355  6609355
total            red: 54.55%    119859329 54477883
...

2021-02-18  Tom de Vries  <tdevries@suse.de>

	PR dwz/26252
	* dwz.c (checksum_ref_die): Undo modifications related to odr.
	(read_debug_info): After calling checksum_ref_die, override
	die_ref_hash for odr DIEs, and recalculate die_ref_hash for all
	other DIEs.