automake: Don't use parallel test harness being the default with automake 1.13

We have no need for the parallel test harness, and we prefer to have the output
of make check on the console

configure.ac

@@ -20,7 +20,17 @@
 # ============================
 
 AC_INIT([strongSwan],[5.1.1])
-AM_INIT_AUTOMAKE([tar-ustar subdir-objects])
+AM_INIT_AUTOMAKE(m4_esyscmd([
+	echo tar-ustar
+	echo subdir-objects
+	case `automake --version | head -n 1` in
+		*" 1.9"*);;
+		*" 1.10"*);;
+		*" 1.11"*);;
+		# don't use parallel test harness in 1.12 and up
+		*) echo serial-tests;;
+	esac
+]))
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES])
 AC_CONFIG_MACRO_DIR([m4/config])
 AC_CONFIG_HEADERS([config.h])