strip: Only sanity check symbols to not discarded sections for debug file.
We can only sanity check the symbols to discarded sections when creating a
debug file. Otherwise we won't keep track of debug_data. This can trigger
erroneously when there are relocation symbols in the symtab for a .debug
section but we are not putting those symbols in a separate .debug file.
Adjust run-strip-test.sh to always run in-place strip size check even
for ET_REL files. Before this fix the sanity check would trigger for
some ET_REL files because they contained such relocation symbols to
.debug sections (but debug_data would be NULL because -f wasn't used).