message: Call out that not all config values can be set via env vars
diff: @@ -190,8 +190,9 @@ variable.
  Environment variables will take precedence over TOML configuration files.
  Currently only integer, boolean, string and some array values are supported to
  -be defined by environment variables. Descriptions below indicate which keys
  -support environment variables.
  +be defined by environment variables. [Descriptions below](#configuration-keys)
  +indicate which keys support environment variables and otherwise they are not
  +supported due to [technicial issues](https://github.com/rust-lang/cargo/issues/5416).
  In addition to the system above, Cargo recognizes a few other specific
  [environment variables][env].
  