bash: improved to use the installed libreadline if possible

shells/bash/bash.conf

@@ -54,6 +54,11 @@ fi
 
 var_append confopt " " "--without-bash-malloc"
 
+# use the installed libreadline if possible
+if pkginstalled readline; then
+	var_append extraconfopt ' ' "--with-installed-readline"
+fi
+
 [ "$SDECFG_PKG_BASH_PROGCOMP" = 0 ] &&
 	var_append confopt " " "--disable-progcomp"
 [ "$SDECFG_PKG_BASH_HELP_CMD" = 0 ] &&