[PATCH] Update auxv cache when there is no auxv cached data

[Luis Machado <luis.machado@arm.com>]

While adding support for MTE corefiles and running the MTE corefile tests,
I noticed a strange situation where loading the symbol file + core file
through the command line has a different behavior compared to firing up
GDB, loading the symbol file with the "file" command and then loading the
core file with the "core" command.

I tracked this down to gdb/auxv.c:get_auxv_inferior_data returning a valid
info struct, but with no auxv data.

We've been doing the auxv caching for a while now, but sometime between
enabling auxv data caching and now, we turned the auxv data into an optional
value.

My guess is that these two modes of opening a symbol file + core file take
slightly different paths in GDB, and in the latter case where we issue
separate "file" and "core" commands, we first cache empty auxv data (no core
file data yet) and later we just return that empty data as if it were valid.

The following patch checks for an empty info->data field, and forces a re-fetch
of auxv data if that is the case.

With this patch, I see full passes for the gdb.arch/aarch64-mte-core testcase.
---
 gdb/auxv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gdb/auxv.c b/gdb/auxv.c
index 8e175138f5d..0d6a860e5f4 100644
--- a/gdb/auxv.c
+++ b/gdb/auxv.c
@@ -361,7 +361,7 @@ get_auxv_inferior_data (struct target_ops *ops)
   struct inferior *inf = current_inferior ();
 
   info = auxv_inferior_data.get (inf);
-  if (info == NULL)
+  if (info == NULL || !info->data.has_value ())
     {
       info = auxv_inferior_data.emplace (inf);
       info->data = target_read_alloc (ops, TARGET_OBJECT_AUXV, NULL);
-- 
2.25.1