Added curl support and one test

Now it checks for the existance of curl after
failing to find wget.

Note that I ended up removing the quotes around $url
when referencing it in the call to wget, since urls can't have spaces
anyways, and the correct quoting was messy.

To test, I did

    rm -r .deps
    make clean
    make cmake
    make

And it worked.

scripts/common.sh

@@ -23,23 +23,31 @@ download() {
 
 	if [ ! -d "$tgt" ]; then
 		mkdir -p "$tgt"
+		local download_command=""
 		if which wget > /dev/null 2>&1; then
-			tmp_dir=$(mktemp -d "/tmp/download_sha1check_XXXXXXX")
-			fifo="$tmp_dir/fifo"
+			# -O - to send output to stdout
+			download_command="wget $url -O -"
+		elif which curl >/dev/null 2>&1; then
+			# -L to follow the redirects that github will send us
+			# -sS to supress the progress bar, but show errors
+			# curl sends output to stdout by default
+			download_command="curl -L -sS $url"
+		else
+			echo "Missing wget utility and curl utility"
+			exit 1
+		fi
+		local tmp_dir=$(mktemp -d "/tmp/download_sha1check_XXXXXXX")
+		local fifo="$tmp_dir/fifo"
 		mkfifo "$fifo"
 		# download, untar and calculate sha1 sum in one pass
-			(wget "$url" -O - | tee "$fifo" | \
+		($download_command | tee "$fifo" | \
 			(cd "$tgt";  tar --strip-components=1 -xvzf -)) &
-			sum=$("$sha1sumcmd" < "$fifo" | cut -d ' ' -f1)
+		local sum=$("$sha1sumcmd" < "$fifo" | cut -d ' ' -f1)
 		rm -rf "$tmp_dir"
 		if [ "$sum" != "$sha1" ]; then
 			echo "SHA1 sum doesn't match, expected '$sha1' got '$sum'"
 			exit 1
 		fi
-		else
-			echo "Missing wget utility"
-			exit 1
-		fi
 	fi
 }