BUILD: Drop clang -Wno-sign-compare

to match GCC and MSVC

Makefile

@@ -52,7 +52,7 @@ endif
 endif
 
 ifeq "$(HAVE_CLANG)" "1"
-	CXXFLAGS+= -Wno-conversion -Wno-shorten-64-to-32 -Wno-sign-compare -Wno-four-char-constants
+	CXXFLAGS+= -Wno-conversion -Wno-shorten-64-to-32 -Wno-four-char-constants
 	# We use a anonymous nested type declaration in an anonymous union in
 	# common/str.h. This is no standard construct and clang warns about it.
 	# It works for all our target systems though, thus we simply disable that