Disable build script for library builds

[DaniPopes]

The build script is only used for emitting the FULL_VERSION environment variable, which is only used in the binary. Make it a noop if "bin" is not enabled.

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #467 will not alter performance

_{Comparing DaniPopes:optional-build (1bcaef5) with main (ca52ac1)}

Summary

✅ 8 untouched benchmarks

[saulshanabrook]

Is the main advantage of this that library builds don't need chrono?

[DaniPopes]

Yeah and that the build script won't do anything. Unfortunately I don't think there is a way to completely disable the build script, but we can make it do the least amount of work possible.