buildsystem: fix gradle download

Current gradle download mechanism has two issues. Assuming, the gradle
download url is:
https://services.gradle.org/distributions/gradle-8.13-bin.zip

1. Compilation script will break if we stop the script amidst the
   download the first time. As next time wget will save the file as:
   gradle-8.13-bin.zip.1, gradle-8.13-bin.zip.2 ... because
   a broken gradle-8.13-bin.zip already exists.

2. For curl to download successfuly from the url, redirection flag
   must be turned on, as it redirects to a different url.

This patch fixes these issues by (1) providing wget the output filename
and (2) turning on redirection for curl using the -L flag.