[Feature Request] Extend sample with support for Release and Debug configurations

[mgrebenets]

Currently the sample is built in what seems to be Debug configuration.
Having support for Release vs Debug would be of great help.

E.g. Release is build with optimizations like -O (speed) or -Osize and -whole-module-optimization.
While Debug is built with SWIFT_COMPILATION_MODE=singlefile (no -whole-module-optimization flag).

Release should be built with DEBUG_INFORMATION_FORMAT = dwarf-with-dsym, which I think means removing -g flag.
No -enable-testing, maybe -DNS_BLOCK_ASSERTIONS=1 if the intention is to turn assertions off for release. No -D DEBUG I guess, etc.

If possible, having a script that packages xcarchive from buck output would be super helpful too. We've got this https://gist.github.com/mgrebenets/8fe4289603aaec0dfeae5eacfae203d6 so far, but it can be improved further and maybe wrapped into/replaced with buck genrule?

[bachand]

Along these lines I also think it would be useful to show how to create an archive from a Buck CLI build that can be used to upload to the App Store, as that proved a bit non-trivial and required some custom tooling. cc: @qyang-nj @shepting