Optmize binary size

[mike-lloyd03]

This PR aims to reduce the size of the compiled dotter binary. I'm taking your advice and including the final binary in my dotfiles but I thought the final binary size was a bit larger than I'd like. I followed the steps here and reduced the file size from 17M to 4.9M.

This PR adds 5 new flags to the release profile in Cargo.toml:

• strip = true: strip symbols
• opt-level = "z": optimize for file size instead of execution speed (more below)
• lto = true: enable Link Time Optimization
• codegen-units = 1: reduces parallel codegen units from 16 to 1
• panic = "abort": prevents unwinding the stack on a panic and prevents displaying a stacktrace

The strip and lto optimizations have no downsizes but the others have some potential negative effects.

Impact on File Size

strip	opt-level	lto	codegen-units	panic	binary size
					17M
X					9.8M
X	X				8.2M
X	X	X			6.0M
X	X	X	X		5.5M
X	X	X	X	X	4.9M

Impact on Execution Time

opt-level can potentially increase execution time. However, I benchmarked cargo test --release using hyperfine and found that there were almost no difference in test time.

hyperfine "cargo test --release"

strip	opt-level	lto	execution time
			165.1 ms ± 11.2 ms
X			164.4 ms ± 19.0 ms
X	X		163.7 ms ± 5.6 ms
X	X	X	170.3 ms ± 24.5 ms

Impact on Build Time

codegen-units = 1 can slow down build times. In my testing, I was building from a clean repo for each run so build times are pretty long. But I think build times will be impacted much less when using cached builds.

hyperfine --prepare "cargo clean" --runs 3 "cargo build --release"

strip	opt-level	lto	codegen-units	panic	build time
					50.777 s ± 0.149 s
X					50.399 s ± 0.195 s
X	X				40.503 s ± 0.017 s
X	X	X			65.934 s ± 0.019 s
X	X	X	X		68.089 s ± 0.554 s
X	X	X	X	X	61.976 s ± 0.434 s

I'm not sure if there's any interest for this kind of PR but I thought I'd throw it out there. Thanks for you review.

[SuperCuber]

Thanks for the well thought out PR! This looks great, and I'll look deeply into it once I get back from work.

Compilation times on release mode are not too bad of a price to pay here since that's mostly done on a (github) release only :)

[SuperCuber]

Looks great, thanks for the contribution!