Suggestion: allow overriding wget

Some OS, for example macOS, does not have wget by default. For my build on macOS I modified the Makefile to use curl -LO in place of wget.

Maybe this detection can be done automatically? Maybe carry a httpget.sh script that finds the appropriate download tool for the OS and calls it? This way the Makefile can call ./httpget.sh url which in turn calls wget url if wget is available, curl -LO url is wget is not available but curl is found, or even some PowerShell on Windows if needed.