Not part of build.

Bug 157298 make install does not work in mozilla/widget/src/gtk2/mai
r=kyle
Thanks for mpeseng@tin.it's fix

widget/src/gtk2/mai/Makefile.in

@@ -72,10 +72,6 @@ CPPSRCS		= \
 EXTRA_DSO_LDOPTS += $(MOZ_GTK2_LIBS) \
 		    -L.. -lwidget_gtk2
 
-# Add you header files need to be exported  here
-EXPORTS		= \
-		$(NULL)
-
 include $(topsrcdir)/config/rules.mk
 
 CFLAGS		+= $(MOZ_GTK2_CFLAGS)