core: fix downloader duplicating downloads

Signed-off-by: Abiola Ibrahim <git@abiosoft.com>

The downloader currently has undesired behaviour of downloading twice
when fetching the possible redirect URL of the asset to be downloaded.

This resolves it by ensuring the initial request is an HEAD request.

util/downloader/download.go

@@ -132,7 +132,7 @@ func (d downloader) downloadFile(r Request) (err error) {
 	}
 
 	// get rid of curl's initial progress bar by getting the redirect url directly.
-	downloadURL, err := d.host.RunOutput("curl", "-Ls", "-o", "/dev/null", "-w", "%{url_effective}", r.URL)
+	downloadURL, err := d.host.RunOutput("curl", "-ILs", "-o", "/dev/null", "-w", "%{url_effective}", r.URL)
 	if err != nil {
 		return fmt.Errorf("error retrieving redirect url: %w", err)
 	}