[Feature]: Detect/handle non-gnu installations of wget

[vhyrro]

wget comes in many shapes and sizes (with the most notable other implementation being busybox), and not every wget allows the same flags. This causes errors like "unable to pull manifest" when a user tries to pull rocks.

It might be interesting to check for the version of wget that is being used during the build stage, or make it very clear in the README to use a GNU version of wget or curl instead.