Read Cargo.toml from target dir

When running `crossgen` on a directory with a missing `Cargo.toml` it
would panic with an error message.

Debugging what happend, I've found it failed to find a `Cargo.toml` file, as it don't exist.
To my surprise, when I've cloned the repo and tried to reproduce using `cargo run -- ~/path/to/my-dir`, there was no panic!

This happened because the `Cargo.toml` was found on `crossgen` repo, not on my targe repo, as expected.

This commit changes the location of the manifest file to use the directory parsed from the arguments.

Signed-off-by: Bruno Tavares <[email protected]>

src/main.rs

@@ -16,6 +16,7 @@ use cargo_toml::TomlManifest;
 use crossgen::Cli;
 use exitfailure::ExitFailure;
 use std::fs::read;
+use std::path::PathBuf;
 use structopt::StructOpt;
 
 fn main() -> Result<(), ExitFailure> {
@@ -27,7 +28,7 @@ fn main() -> Result<(), ExitFailure> {
   let name = args.name()?;
   let lib = args.lib();
 
-  let manifest = TomlManifest::from_slice(&read("Cargo.toml")?)?;
+  let manifest = TomlManifest::from_slice(&read(dir.join("Cargo.toml"))?)?;
   let repo = manifest
     .package
     .repository