Cargo Features

[dependencies]
nss-gk-api = { version = "0.3.0", default-features = false, features = ["deny-warnings", "gecko"] }
default = deny-warnings

The deny-warnings feature is set by default whenever nss-gk-api is added without default-features = false somewhere in the dependency tree.

deny-warnings default
gecko = mozbuild

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.

mozbuild build gecko?