Pass target to compilation time.

[WenheLI]

Make sure these boxes are checked! 📦✅

• [ x] You have the latest version of rustfmt installed

$ rustup component add rustfmt

• [x ] You ran cargo fmt on the code base before submitting
• [x ] You reference which issue is being closed in the PR text

This PR is to provide the function that we can pass the target to compilation time.
See #795

[niko-ng]

Hello,
Any news about merging that? I also need this feature, so I am stuck with using the branch of that PR, and cannot benefit from the recent bug fixes...