Cargo Features

libdeflate-sys has no features set by default.

[dependencies]
libdeflate-sys = { version = "1.20.0", features = ["freestanding", "dynamic"] }
freestanding
dynamic = pkg-config

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

pkg-config build dynamic?