Retry downloading of depends sources 3 times

Author: codablock

ci/build_depends.sh

@@ -26,4 +26,17 @@ if [ -n "$OSX_SDK" ]; then
   fi
 fi
 
+# Let's first download all source packages and retry 3 times on failure (thank you Travis...)
+success=false
+for i in $(seq 1 3); do
+	if make -C depends download; then
+		success=true
+		break
+	fi
+	sleep 5
+done
+if [ "$success" != "true" ]; then
+	exit 1
+fi
+
 make $MAKEJOBS -C depends HOST=$HOST $DEP_OPTS