[Makefile] use some variable trick to define package_bin instead of double-colon rule (see #5240)

Makefile

@@ -17,6 +17,8 @@ INSTALL_STD_DIR=$(INSTALL_LIB_DIR)/std
 PACKAGE_OUT_DIR=out
 PACKAGE_SRC_EXTENSION=.tar.gz
 
+PLATFORM?=unix
+
 OUTPUT=haxe
 EXTENSION=
 OCAMLOPT?=ocamlopt
@@ -252,7 +254,7 @@ package_src:
 	curl -s https://raw.githubusercontent.com/Kentzo/git-archive-all/1.12/git-archive-all -o extra/git-archive-all
 	python extra/git-archive-all $(PACKAGE_OUT_DIR)/$(PACKAGE_FILE_NAME)_src$(PACKAGE_SRC_EXTENSION)
 
-package_bin::
+package_unix:
 	mkdir -p $(PACKAGE_OUT_DIR)
 	rm -rf $(PACKAGE_FILE_NAME) $(PACKAGE_FILE_NAME).tar.gz
 	# Copy the package contents to $(PACKAGE_FILE_NAME)
@@ -262,6 +264,7 @@ package_bin::
 	tar -zcf $(PACKAGE_OUT_DIR)/$(PACKAGE_FILE_NAME)_bin.tar.gz $(PACKAGE_FILE_NAME)
 	rm -r $(PACKAGE_FILE_NAME)
 
+package_bin: package_$(PLATFORM)
 
 install_dox:
 	haxelib git hxparse https://github.com/Simn/hxparse development src

Makefile.win

@@ -1,5 +1,5 @@
+PLATFORM=win
 include Makefile
-
 OUTPUT=haxe.exe
 EXTENSION=.exe
 PACKAGE_SRC_EXTENSION=.zip
@@ -36,7 +36,7 @@ CC_CMD=($(OCAMLOPT) $(ALL_CFLAGS) -c $< 2>tmp.cmi && $(FILTER)) || ($(FILTER) &&
 CC_PARSER_CMD=($(OCAMLOPT) -pp camlp4o $(ALL_CFLAGS) -c src/syntax/parser.ml 2>tmp.cmi && $(FILTER)) || ($(FILTER) && exit 1)
 endif
 
-package_bin::
+package_win:
 	mkdir -p out
 	rm -rf $(PACKAGE_FILE_NAME) $(PACKAGE_FILE_NAME).zip temp.zip
 	# Copy the package contents to $(PACKAGE_FILE_NAME)