fbc: tests/cpp/*.bmk, add warnings and ignore calling convention attributes with '-Wall -Wno-attributes'

Author: jayrm

tests/cpp/class.bmk

@@ -7,4 +7,4 @@ EXTRA_OBJS := class-cpp.o
 
 $(SRCDIR)class-cpp.o : $(SRCDIR)class-cpp.cpp
 	# Pass $(CFLAGS) to get -m32 or -m64 as required
-	$(CXX) -c $(CFLAGS) -o $@ $^
+	$(CXX) -c $(CFLAGS) -Wall -Wno-attributes -o $@ $^