fix flow-parser-bin's make dist on OS X

Summary:
OS X's `cp` doesn't support the `-u` flag, so do it in bash manually.

also realized that `make download` redownloads the release tarballs every time, which updates their mtimes, which causes everything downstream to be redone. since the release tarballs are immutable, we don't need to redownload them if they exist. this will also allow Circle to use its local copies, rather than uploading them to github in one step and then downloading them from github in the next.

Reviewed By: gabelevi

Differential Revision: D7518852

fbshipit-source-id: c8d94d2a3e73aa4d770a39460e2ab8b561d3f7da

Author: mroch

packages/flow-parser-bin/Makefile

@@ -43,7 +43,7 @@ clean:
 # `make download` hasn't been run.
 $(addsuffix .dl,$(RELEASE_ZIPS)):
 	@mkdir -p "$(@D)"
-	curl --max-time 300 \
+	[ -e "$(subst .dl,,$@)" ] || curl --max-time 300 \
 		-L "$(patsubst dist/release/%.zip.dl,$(HOST)/%-v$(FLOW_VERSION).zip,$@)" \
 		-o "$(subst .dl,,$@)" || rm "$(subst .dl,,$@)"
 
@@ -53,7 +53,8 @@ $(addsuffix .dl,$(RELEASE_ZIPS)):
 dist/local/libflowparser-$(PLATFORM).zip:
 	@mkdir -p "$(@D)"
 	$(MAKE) -C ../../src/parser dist/libflowparser.zip
-	cp -u ../../src/parser/dist/libflowparser.zip "$@"
+	[ ! -e "$@" -o "../../src/parser/dist/libflowparser.zip" -nt "$@" ] && \
+		cp ../../src/parser/dist/libflowparser.zip "$@"
 
 # The following two "pattern" rules (because of the %) choose between using
 # the downloaded release builds or building from source, depending on whether
@@ -64,10 +65,10 @@ dist/local/libflowparser-$(PLATFORM).zip:
 # kicks off the local build.
 dist/libflowparser-%.zip: dist/release/libflowparser-%.zip
 	@mkdir -p "$(@D)"
-	cp -u "$<" "$@"
+	cp "$<" "$@"
 dist/libflowparser-%.zip: dist/local/libflowparser-%.zip
 	@mkdir -p "$(@D)"
-	cp -u "$<" "$@"
+	cp "$<" "$@"
 
 $(LIBS): lib/%/libflowparser.a: dist/libflowparser-%.zip
 	DIR="$(basename $<)"; \