Cargo.toml: Turn on link-time optimisation

Thanks to Lifthrasiir for the detailed information about reducing Rust
compiled binary size:
https://lifthrasiir.github.io/rustlog/why-is-a-rust-executable-large.html

Using link-time optimisation gets our release build built with

    cargo build --release

down from 13 Mb to 2 Mb. Pretty good.

Using

    RUSTFLAGS="-C opt-level=s" cargo build --release
    # or
    RUSTFLAGS="-C opt-level=z" cargo build --release

brought it down additionally to 1.9 Mb. Still trying to decide if I want
to keep that. Think I might, but will add it later.

1 files changed, 3 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 905af39..8b82c16 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,3 +18,6 @@ cbindgen = "0.6.2"
 
 [lib]
 crate-type = ["staticlib"]
+
+[profile.release]
+lto = true