tools: use curl --retry to download tarballs

If some URLs are flaky we have a better chance of not failing a build.
(like GNU mirrors and git)

We don't need a temporary file, we let curl manage the output file and
overwrite it when necessary. If anything the hash will not match.

(cherry picked from commit ded9e6c5d9)

extras/tools/tools.mak

@@ -10,7 +10,7 @@ TARBALLS := $(TOOLS)
 #
 
 ifeq ($(shell command -v curl >/dev/null 2>&1 || echo FAIL),)
-download = curl -f -L -- "$(1)" > "$@.tmp" && touch $@.tmp && mv $@.tmp $@
+download = curl -f -L --retry 3 --output "$@" -- "$(1)"
 else ifeq ($(shell command -v wget >/dev/null 2>&1 || echo FAIL),)
 download = rm -f $@.tmp && \
 	wget --passive -c -p -O $@.tmp "$(1)" && \