Use built local on CI and not LKG

[weswigham]

Should prevent the nightly publish from failing again from us being unable to built ourselves with the current snapshot again~

[weswigham]

Note: This PR should fail until I add another commit to fix the build break.

[weswigham]

Okay, and that should fix our build.

@ahejlsberg should we look into why

    export function assign<T extends object>(t: T, ...args: (T | undefined)[]) {
        for (const arg of args) {
            for (const p in arg!) {
                if (hasProperty(arg!, p)) {
                    t![p] = arg![p]; // TODO: GH#23368
                }
            }
        }
        return t;
    }

no longer typechecks (or should we call this acceptable)? I'd assume the cause if one of #29847, #29787, or #29858 - I'd wager the last, given this is a function with a rest parameter. It seems like we're wrapping the type with an excess NonNullable alias which, since they don't compose and simplify, makes the assignment fail. It may equally be worth making getGlobalNonNullableTypeInstantiation not wrap something which is already an instance of NonNullable with another layer of it to avoid the issue for now.

[rbuckton]

Do we need the TODO anymore?

[weswigham]

mm the comment isn't relevant, but the issue still stands.

[ahejlsberg]

@weswigham I suspect the build break was caused by #27697, but a contributing factor appears to be some code that was added in #28348 to add non-nullability to the right hand expression in a for-in statement. That code behaves differently than a corresponding narrowing comparison with null or undefined which is why you could fix the issue by adding an if statement.

[weswigham]

Mmm very possibly, we don't publish nightlies on weekends, but I forgot to include the things merged over the weekend in the candidates for the failure. In any case, I believe #29437 plus the enhancements to empty intersection calculations with type parameters in the negated types PR would fix the issue (as NonNullable<T> would simplify to T as T extends object).