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.

Signed-off-by: Patrick Steinhardt <ps@pks.im>

libraries/libapparmor/src/libapparmor.map

@@ -127,6 +127,7 @@ APPARMOR_3.0 {
 PRIVATE {
 	global:
 		_aa_is_blacklisted;
+		_aa_asprintf;
 		_aa_autofree;
 		_aa_autoclose;
 		_aa_autofclose;