libcr51sign: Fixes for compiler warnings

Change-Id: I4053720365be81fff02aebbcf8f0e95d34fe87d9
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/subprojects/libcr51sign/meson.build b/subprojects/libcr51sign/meson.build
index 66f77f0..f122686 100644
--- a/subprojects/libcr51sign/meson.build
+++ b/subprojects/libcr51sign/meson.build
@@ -19,7 +19,7 @@
   meson_version: '>=0.57.0',
   default_options: [
     'warning_level=3',
-    'werror=false',
+    'werror=true',
     'c_std=c18',
   ])