url: use always busybox wget

I think there used to be problems with using http_proxy on bb wget,
but those have been fixed for quite some time. This fixes #347.
We should probably use libcurl or similar library eventually, but
I'm not entirely sure if/when we want that.

src/url.c

@@ -70,7 +70,7 @@ static int fork_wget(const char *url, pid_t *ppid)
 		close(fds[0]);
 		dup2(open("/dev/null", O_RDONLY), STDIN_FILENO);
 		dup2(fds[1], STDOUT_FILENO);
-		execlp("wget", "wget", "-q", "-O", "-", url, NULL);
+		execlp("busybox", "wget", "-q", "-O", "-", url, NULL);
 		exit(0);
 	}