make effc compilation optional

Makefile

@@ -1,16 +1,16 @@
-# Extended C++ warning policy
-CXXFLAGS += -Werror -Wall -Wextra -Wshadow -Wpedantic -Wformat-nonliteral \
-            -Wformat-security -Wswitch-default -Wuninitialized -Wundef \
-            -Wpointer-arith -Woverloaded-virtual -Wctor-dtor-privacy \
-            -Wnon-virtual-dtor -Woverloaded-virtual -Wsign-promo \
-            -Wno-unused-parameter -Weffc++
-
 all: xmltest staticlib
 
 rebuild: clean all
 
 xmltest: xmltest.cpp libtinyxml2.a
 
+effc:
+	gcc -Werror -Wall -Wextra -Wshadow -Wpedantic -Wformat-nonliteral \
+        -Wformat-security -Wswitch-default -Wuninitialized -Wundef \
+        -Wpointer-arith -Woverloaded-virtual -Wctor-dtor-privacy \
+        -Wnon-virtual-dtor -Woverloaded-virtual -Wsign-promo \
+        -Wno-unused-parameter -Weffc++ xmltest.cpp tinyxml2.cpp -o xmltest
+
 clean:
 	$(RM) *.o xmltest libtinyxml2.a