Remove -Werror

Index: CMakeLists.txt
--- CMakeLists.txt.orig
+++ CMakeLists.txt
@@ -182,7 +182,6 @@ if(NOT MSVC)
 		-Wall
 		-Wextra
 		#-Wshadow  # Note: Candy Crisis goes crazy with shadowing
-		-Werror=return-type
 		-Wstrict-aliasing=2
 		-Wno-multichar
 	)
