From b05cd9e5c65c88720fa8ab5d96ef2e887ad8b761 Mon Sep 17 00:00:00 2001
From: Graham Mainwaring <graham@mhn.org>
Date: Wed, 2 Nov 2016 13:46:49 -0400
Subject: [PATCH] Can't use bash syntax since make uses /bin/sh

---
 Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 8b79000e06..80b8f61a9a 100644
--- a/Makefile
+++ b/Makefile
@@ -239,7 +239,7 @@ clean: clean-rpm clean-deb clean-ui clean-tar clean-packer clean-bundle
 
 # convenience target to assert environment variables are defined
 guard-%:
-	@if [ "${${*}}" == "" ]; then \
+	@if [ "$${$*}" = "" ]; then \
 	    echo "The required environment variable '$*' is not set"; \
 	    exit 1; \
 	fi