Adapt error messages in tests/scripts/list-*
diff --git a/tests/scripts/list-macros.sh b/tests/scripts/list-macros.sh
index b194831..7385946 100755
--- a/tests/scripts/list-macros.sh
+++ b/tests/scripts/list-macros.sh
@@ -1,6 +1,11 @@
 #!/bin/sh
 
-set =eu
+set -eu
+
+if [ -d include/mbedtls ]; then :; else
+    echo "$0: must be run from root" >&2
+    exit 1
+fi
 
 HEADERS=$( ls include/mbedtls/*.h )