Insufficient escaping in code generator

[kornelski]

Code generator doesn't escape strings:

https://github.com/rustyhorde/vergen/blob/master/src/output/codegen.rs#L23

Adding quotes around the value is not sufficient - the value could contain quotes or end with backslash, and cause the value to become arbitrary Rust source code.

With the current set of inputs I don't think it's a real vulnerability, but it does increase risk of creating one if some more arbitrary build info was added in the future.

[teor2345]

Rather than trying to escape string terminators and backslashes, it would be more reliable to just delete those characters.