Create Resources directory dynamically at compile time

The 'Resources' directory is used in macOS development to test the binary
without building TuxPaint.app bundle, which is helpful for rapid application
development since creating the app bundle takes a long time.

It's been reported that the symlink in the Resources directory was causing the
'release' target to copy the files in the 'data' directory twice into the
source release tarball.

This change removes the static Resources directory but creates it dynamically
when the 'tuxpaint' target is built and removes it via 'clean' target so the
'release' target does not copy the files in the 'data' directory into the
source release tarball twice.

Makefile

@@ -83,6 +83,9 @@ RSRC_CMD:=$($(OS)_RSRC_CMD)
 beos_MIMESET_CMD:=mimeset -f tuxpaint
 MIMESET_CMD:=$($(OS)_MIMESET_CMD)
 
+macos_RAD_CMD:=[[ ! -d Resources/share ]] && mkdir -p Resources/share && ln -s ../../data Resources/share/tuxpaint || :
+RAD_CMD:=$($(OS)_RAD_CMD)
+
 windows_SO_TYPE:=dll
 macos_SO_TYPE:=dylib
 beos_SO_TYPE:=so
@@ -607,7 +610,7 @@ clean:
 	@-rm -f templates/.thumbs/*.png
 	@if [ -d templates/.thumbs ]; then rmdir templates/.thumbs; fi
 	@-if [ "x$(BUNDLE)" != "x" ]; then rm -rf $(BUNDLE); fi
-	@-rm -f TuxPaint.dmg temp.dmg; rm -rf magic/*.dSYM
+	@-rm -f TuxPaint.dmg temp.dmg; rm -rf magic/*.dSYM Resources
 	@echo
 
 # "make uninstall" should remove the various parts from their
@@ -1052,6 +1055,7 @@ tuxpaint:	obj/tuxpaint.o obj/i18n.o obj/im.o obj/cursor.o obj/pixels.o \
 	$(CC) $(CFLAGS) $(LDFLAGS) $(DEBUG_FLAGS) $(SDL_CFLAGS) $(FRIBIDI_CFLAGS) $(DEFS) \
 		-o tuxpaint $^ \
 		$(SDL_LIBS) $(SVG_LIB) $(ARCH_LINKS)
+	@$(RAD_CMD)
 	@$(RSRC_CMD)
 	@$(MIMESET_CMD)