Empty the pg_config system information view. This view keeps references to
several -dev outputs, which we want to avoid to keep closure size down.

The alternative to this patch would be to nuke references across the board,
but this will also affect the output of the pg_config utility. By emptying
the view only, we keep the pg_config binary intact. It resides in the -dev
output, so it's fine to have all those references there.

---
--- a/src/backend/utils/misc/pg_config.c
+++ b/src/backend/utils/misc/pg_config.c
@@ -69,16 +69,6 @@ pg_config(PG_FUNCTION_ARGS)
 	/* initialize our tuplestore */
 	tupstore = tuplestore_begin_heap(true, false, work_mem);
 
-	configdata = get_configdata(my_exec_path, &configdata_len);
-	for (i = 0; i < configdata_len; i++)
-	{
-		values[0] = configdata[i].name;
-		values[1] = configdata[i].setting;
-
-		tuple = BuildTupleFromCStrings(attinmeta, values);
-		tuplestore_puttuple(tupstore, tuple);
-	}
-
 	/*
 	 * no longer need the tuple descriptor reference created by
 	 * TupleDescGetAttInMetadata()
--- a/src/test/regress/expected/sysviews.out
+++ b/src/test/regress/expected/sysviews.out
@@ -20,7 +20,7 @@ select count(*) >= 0 as ok from pg_available_extensions;
 (1 row)
 
 -- At introduction, pg_config had 23 entries; it may grow
-select count(*) > 20 as ok from pg_config;
+select count(*) = 0 as ok from pg_config;
  ok 
 ----
  t
--- a/src/test/regress/sql/sysviews.sql
+++ b/src/test/regress/sql/sysviews.sql
@@ -13,7 +13,7 @@ select count(*) >= 0 as ok from pg_available_extension_versions;
 select count(*) >= 0 as ok from pg_available_extensions;
 
 -- At introduction, pg_config had 23 entries; it may grow
-select count(*) > 20 as ok from pg_config;
+select count(*) = 0 as ok from pg_config;
 
 -- We expect no cursors in this test; see also portals.sql
 select count(*) = 0 as ok from pg_cursors;