Only build nip2-icon.o on Windows

Don't generate and build dummy.c on other platforms.  Fixes warning
when building on MacPorts:

    dummy.c:1:14: warning: control reaches end of non-void function [-Wreturn-type]

Also fixes "make dist" failure if run before "make":

    make[2]: *** No rule to make target '../src/dummy.c', needed by 'nip2.pot'.  Stop.

Author: bgilbert

.gitignore

@@ -30,7 +30,6 @@ po/POTFILES
 fred
 po/Makefile.in.in
 src/.deps/
-src/dummy.c
 src/gtksheet-marshal.c
 src/gtksheettypebuiltins.c
 src/lex.c

po/POTFILES.in

@@ -40,7 +40,6 @@ src/parse.c
 src/managedgvalue.c
 src/conversion.c
 src/trace.c
-src/dummy.c
 src/gtkutil.c
 src/slider.c
 src/action.c

src/Makefile.am

@@ -184,7 +184,6 @@ nip2_SOURCES = \
 	plotwindow.h \
 	model.c \
 	model.h \
-	nip2-icon.rc \
 	option.c \
 	option.h \
 	optionview.c \
@@ -296,6 +295,11 @@ nip2_SOURCES = \
 	workspaceview.c \
 	workspaceview.h 
 
+if OS_WIN32
+nip2_SOURCES += \
+	nip2-icon.rc
+endif
+
 helpindex.h: 
 	./makehelpindex.pl $(prefix) > helpindex.h
 nipmarshal.h:
@@ -305,13 +309,8 @@ nipmarshal.c:
 	glib-genmarshal --prefix=nip --body nipmarshal.list >> nipmarshal.c
 
 .rc.o:
-if OS_WIN32 
 	cp ${top_srcdir}/share/nip2/data/nip2-icon.ico .
 	${WINDRES} $< -o $@ 
-else
-	echo "int poop () {}" >dummy.c 
-	$(CC) -c dummy.c -o $@
-endif
 
 # we have to replace the standard .y.c rule: we are a bison-only GLR parser,
 # so we can't use autoconf's preferred -y yacc-compatibility stuff