[ci] Actually generate chksum file

scripts/prep_deploy.sh

@@ -5,3 +5,5 @@ mkdir $name
 cp target/$TARGET/release/sccache $name/
 cp README.md LICENSE $name/
 tar czvf $name.tar.gz $name
+chksum=($(shasum -ba 256 $name.tar.gz))
+echo "$chksum" > $name.tar.gz.sha256