customized pkg-config is incomplete?

[igorbernstein]

Hi,

I'm fairly new to rust and cross compilation in general, so I apologize if I'm misunderstanding something. But it seems like #86 is incomplete. It seems like it checks if PKG_CONFIG_<triple> is set to enable cross compilation, but doesn't actually use the wrapper script defined by that env var when constructing the command:

pkg-config-rs/src/lib.rs

Lines 396 to 398 in 5432578

	let exe = self
	.env_var_os("PKG_CONFIG")
	.unwrap_or_else(|| OsString::from("pkg-config"));

I believe that should be changed to:

            self.targetted_env_var("PKG_CONFIG")

[sdroege]

I think so too, thanks for checking! Do you want to provide a PR for this?