Enable Link-Time Optimization (LTO)

[zamazan4ik]

Is your feature request related to a problem? Please describe.
It's not a problem - it's an improvement idea

Describe the solution you'd like
I noticed that Link-Time Optimization (LTO) is not enabled for Nickel. I suggest switching it on since it will reduce the binary size (always a good thing to have) and will likely improve the application's performance (its CPU part). If you want to read more about LTO, I can recommend starting from this Rustc documentation.

I suggest enabling LTO only for the Release builds so as not to sacrifice the developers' experience while working on the project since LTO consumes an additional amount of time to finish the compilation routine. If you think that a regular Release build should not be affected by such a change as well, then I suggest adding an additional dist or release-lto profile where in addition to regular release optimizations LTO will also be added. Such a change simplifies life for maintainers and others interested in the project persons who want to build the most performant version of the application. Using ThinLTO should also help to reduce the build-time overhead with LTO. E.g., check cargo-outdated Release profile.

Basically, it can be enabled with the following lines:

[profile.release]
lto = true

I have made quick tests (Fedora 41, Rustc 1.82) by adding lto = true to the Release profile. The binary size reduction is the following:

• nickel: from 28 Mib to 24 Mib
• nls: from 18 to 16 Mib

Describe alternatives you've considered
N/A

Additional context
N/A

[yannham]

Hello,

I guess enabling LTO is a low-hanging fruit for release builds. I can't think of a good reason against it. We just have to make sure it's configurable so that the CI doesn't perform LTO, where it's useless. Maybe a dedicated cargo target that is like release but with LTO enabled would be enough.