build: Remove unused script

* http_prebuilt.mk appears to be long gone.

Change-Id: I8ca584fc1e468bb47164984bb363f0cf29750e68
diff --git a/build/tasks/http_curl_prebuilt.sh b/build/tasks/http_curl_prebuilt.sh
deleted file mode 100755
index c90c35f..0000000
--- a/build/tasks/http_curl_prebuilt.sh
+++ /dev/null
@@ -1,6 +0,0 @@
-#!/bin/bash
-
-url=$1
-output=$2
-
-curl -L "$url" --create-dirs -o $output --compressed -H "Accept-Encoding: gzip,deflate,sdch" && exit 0 || exit 1