strip: Files with symbols referring to non-existing sections are illformed

The check added in commit 4540ea98c "strip: Fix check test for SHN_XINDEX
symbol" was not complete. The (extended) section index should also exist.
If it doesn't exist, mark the file as illformed.

https://sourceware.org/bugzilla/show_bug.cgi?id=24385

Signed-off-by: Mark Wielaard <mark@klomp.org>
2 files changed