build cppunit also with STL debug when STL debug is enabled

http://lists.freedesktop.org/archives/libreoffice/2011-July/014970.html

cppunit/makefile.mk

@@ -117,6 +117,10 @@ OUT2LIB = ooo-install/lib/libcppunit.dll.a
 MY_LIBS = -lm
 .END
 
+.IF "$(ENABLE_DEBUG_STL)" == "TRUE"
+EXTRA_CFLAGS += -D_GLIBCXX_DEBUG
+.ENDIF
+
 CONFIGURE_ACTION = ./configure
 
 .IF "$(debug)"!=""