libapparmor: add _aa_asprintf to private symbols

While `_aa_asprintf` is supposed to be of private visibility, it's used
by apparmor_parser and thus required to be visible when linking. This
commit thus adds it to the list of private symbols to make it available
for linking in apparmor_parser.

MR: https://gitlab.com/apparmor/apparmor/-/merge_requests/643
Signed-off-by: Patrick Steinhardt <ps@pks.im>
(cherry picked from commit 9a8fee6bf1)

libraries/libapparmor/src/libapparmor.map

@@ -90,6 +90,7 @@ APPARMOR_2.10 {
 PRIVATE {
 	global:
 		_aa_is_blacklisted;
+		_aa_asprintf;
 		_aa_autofree;
 		_aa_autoclose;
 		_aa_autofclose;