BUILD_ALLOW_MIDL_WARNINGS was placed outside ifdef block and was stuck as always defined. This issue is fixed in this commit.

Author: stephanosio

makefile.def

@@ -95,8 +95,8 @@ USER_ENV_BROWSER_INFO=1
 !ifdef BUILD_ALLOW_ALL_WARNINGS
 BUILD_ALLOW_LINKER_WARNINGS=1
 BUILD_ALLOW_COMPILER_WARNINGS=1
-!endif
 BUILD_ALLOW_MIDL_WARNINGS=1
+!endif
 
 !ifndef BUILD_ALLOW_LINKER_WARNINGS
 LINKER_WX_SWITCH=/WX