Improve space performance of swiftly binaries

[cmcgee1024]

The swiftly binaries can be quite large. Decreasing their size can improve download times, especially over slower connections.

It is possible that these linker flags could yield smaller binaries for swiftly:

--experimental-lto-mode=full -Xswiftc -experimental-hermetic-seal-at-link

[xtremekforever]

Is -experimental-hermetic-seal-at-link working for Linux ELF binaries yet?

[rauhul]

I've only ever used it for macho