Test if versions in build.zon and build.zig.zon match.

[AndrewKraevskii]

As can be seen without testing they became out of sync and with new ability to import zon files it's pretty easy to do.

[AndrewKraevskii]

Actually what was the original reason to place this data in two places? Maybe we should remove copy from build.zig and just use one from build.zig.zon?

[leecannon]

I agree that the version in the zon should be the only one.

[AndrewKraevskii]

I agree that the version in the zon should be the only one.

Done

[Techatrix]

The minimum_build_zig_version in the build.zig is not necessarily the same as the minimum_zig_version in the build.zig.zon. As I tried to explain in the doc comments, the minimum_zig_version must be a version that can be downloaded from ziglang.org or a mirror which is why it it sometimes a more recent version than minimum_build_zig_version that generally points to the exact commit that introduced a breaking change. The documentation doesn't clearly spell out this difference so I see how the confusion arises.

Nonetheless, the change is fine except that the doc comments for minimum_build_zig_version should be moved to build.zig.zon which I will take care of.

If anyone is wondering why the version was duplicated in two files in the first place, see #2421.