Use new Rustc/Cargo 1.58.0 strip feature in the pkg build

[ximon18]

Currently the pkg build manually invokes strip on built binaries. However the pkg build uses latest stable Rust and Rust 1.58.0 released two days from now will bring with it the new support for specifying binary stripping in the [profile.release] section of Cargo.toml. Using this will be less custom and hopefully will also be supported by cargo cross cross-compiled builds which otherwise require manually specifying the right strip tool to use.

[ximon18]

Update: In a quick local test using cross build the resulting binary was significantly smaller when built with cross +nightly build and the following addition to Cargo.toml (26233520 bytes for krill vs 34970356 bytes):

[profile.release]
panic = "abort"
+strip = "symbols"

[ximon18]

This will not actually be available via Cargo in 1.58.0, rather in the next release. See rust-lang/rust#72110 (comment).