fix issue 18981: SIGSEGV during backtrace when debug info is compressed

[yshui]

Detect compressed debug line section, do not try to resolve line numbers if
the debug info is compressed.

Side note: seems I could not get line number no matter the debug info is compressed or not, is that a bug?

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	18981	enhancement	SIGSEGV during backtrace when debug info is compressed

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub fetch digger
dub run digger -- build "master + druntime#2214"

[JinShil]

Side note: seems I could not get line number no matter the debug info is compressed or not, is that a bug?

Probably https://issues.dlang.org/show_bug.cgi?id=18068

[wilzbach]

AFAICT there's no reason for this special casing here. FreeBSD and DragonflyBSD also use the same ELF format and thus imho it's better to add the SHF_COMPRESSED constant to the respective files.

[yshui]

@wilzbach Fixed