Allow *.make to contain tabs

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/scripts/check_files.py b/tests/scripts/check_files.py
index a93b825..f6f6d6c 100755
--- a/tests/scripts/check_files.py
+++ b/tests/scripts/check_files.py
@@ -318,6 +318,7 @@
 
     heading = "Tabs present:"
     suffix_exemptions = frozenset([
+        ".make",
         ".pem", # some openssl dumps have tabs
         ".sln",
         "/Makefile",