[BPF] add missing attribute in pragma-attribute-supported-attributes-list.test

Add the newly supported BPF specific __attribute__((preserve_access_index)
in the pragma-attribute-supported-attributes-list.test.

Author: yonghong-song

clang/test/Misc/pragma-attribute-supported-attributes-list.test

@@ -20,6 +20,7 @@
 // CHECK-NEXT: ArmMveAlias (SubjectMatchRule_function)
 // CHECK-NEXT: AssumeAligned (SubjectMatchRule_objc_method, SubjectMatchRule_function)
 // CHECK-NEXT: Availability ((SubjectMatchRule_record, SubjectMatchRule_enum, SubjectMatchRule_enum_constant, SubjectMatchRule_field, SubjectMatchRule_function, SubjectMatchRule_namespace, SubjectMatchRule_objc_category, SubjectMatchRule_objc_implementation, SubjectMatchRule_objc_interface, SubjectMatchRule_objc_method, SubjectMatchRule_objc_property, SubjectMatchRule_objc_protocol, SubjectMatchRule_record, SubjectMatchRule_type_alias, SubjectMatchRule_variable))
+// CHECK-NEXT: BPFPreserveAccessIndex (SubjectMatchRule_record)
 // CHECK-NEXT: CFAuditedTransfer (SubjectMatchRule_function)
 // CHECK-NEXT: CFConsumed (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: CFICanonicalJumpTable (SubjectMatchRule_function)