From 1ca277d914bb4775af452edbf5c6d5ecddabceb4 Mon Sep 17 00:00:00 2001
From: Kaspar Schleiser <kaspar@schleiser.de>
Date: Thu, 14 Nov 2019 12:12:18 +0100
Subject: [PATCH] make: enable SECONDEXPANSION for module/application builds

---
 Makefile.base | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Makefile.base b/Makefile.base
index 8f13e7d3b2..27eda61550 100644
--- a/Makefile.base
+++ b/Makefile.base
@@ -2,6 +2,15 @@ ifeq (, $(__RIOTBUILD_FLAG))
   $(error You cannot build a module on its own. Use "make" in your application's directory instead.)
 endif
 
+#
+# enable second expansion of prerequisites.
+#
+# Doing that here enables it globally for all modules and the application.
+#
+# See https://www.gnu.org/software/make/manual/html_node/Secondary-Expansion.html
+# for what it can be used for.
+.SECONDEXPANSION:
+
 unexport DIRS
 DIRS := $(sort $(abspath $(DIRS)))