Prefer mold linker on Linux

[AMythicDev]

Currently, fleet uses zld on MacOS and lld on Linux and Windows. A better alternative on Linux would be mold as it is even faster than lld.

Please refer to the mold's README to get some real benchmarks on the performance difference.

It wouldn't be recommended to use it on Windows as it's support for Windows is still being worked on but we can for sure use it on Linux.

[Milo123459]

I don't think Mold is stable enough? It's still in the alpha stages of the project.

[VarunPotti]

We did look into mold but we decided to drop it as it is not stable yet (and all the resources we could find on installation told that the end user had to build from source). However we will be introducing more customization options so that you can set the type of linker you would want to use on your projects!

[suptejas]

Our license is not compatible with that of mold, which is why we were forced to drop it as an option.

Edit: I might be wrong about this.