Consider distributing release + LTO binary

[ishitatsuyuki]

The current rustup-init binary is 9.3M in size, while it shouldn't be so big to bootstrap (you need to download 10M before even seeing a message.) It seems to contain debug symbols too.

Building with release resulted in 5.0M binary, with LTO it's 4.9M (doesn't make much sense). This halves download, and makes the experience better.

[brson]

Yes please. Patches wanted.

[remram44]

Adding lto=true, panic=abort I didn't actually see much of an improvement: https://github.com/remram44/rustup.rs/commit/45342602d142b75a685002d8f64d6d2233c08c7f And reading CI scripts, isn't this already building as release?

How did you get those down to 5MB?

[ishitatsuyuki]

This is the result of my local toolchain (glibc, nightly). I'm not sure which configuration it uses for CI.