waf: make initialiser reordering fatal

we were bitten by a nasty bug in CAN because of constructor reordering

Tools/ardupilotwaf/boards.py

@@ -361,10 +361,10 @@ class Board:
             '-Wpointer-arith',
             '-Wno-unused-parameter',
             '-Wno-missing-field-initializers',
-            '-Wno-reorder',
             '-Wno-redundant-decls',
             '-Wno-unknown-pragmas',
             '-Wno-expansion-to-defined',
+            '-Werror=reorder',
             '-Werror=cast-align',
             '-Werror=attributes',
             '-Werror=format-security',