[lldb] Revive shell test after updating UnwindTable (#86770)

In
     commit 2f63718f8567413a1c596bda803663eb58d6da5a
     Author: Jason Molenda <jmolenda@apple.com>
     Date:   Tue Mar 26 09:07:15 2024 -0700

[lldb] Don't clear a Module's UnwindTable when adding a SymbolFile
(#86603)

I stopped clearing a Module's UnwindTable when we add a SymbolFile to
avoid the memory management problems with adding a symbol file
asynchronously while the UnwindTable is being accessed on another
thread. This broke the target-symbols-add-unwind.test shell test on
Linux which removes the DWARF debub_frame section from a binary, loads
it, then loads the unstripped binary with the DWARF debug_frame section
and checks that the UnwindPlans for a function include debug_frame.

I originally decided that I was willing to sacrifice the possiblity of
additional unwind sources from a symbol file because we rely on assembly
emulation so heavily, they're rarely critical. But there are targets
where we we don't have emluation and rely on things like DWARF
debug_frame a lot more, so this probably wasn't a good choice.

This patch adds a new UnwindTable::Update method which looks for any new
sources of unwind information and adds it to the UnwindTable, and calls
that after a new SymbolFile has been added to a Module.

GitOrigin-RevId: 6a0ec8e25cba9d398cf525889c53835cf40247a3
4 files changed