Un-delete "bottle block".

Q.v. https://github.com/Homebrew/homebrew/pull/28689#discussion_r11978052
Prefer &&/||/! over and/or/not.

Q.v. https://github.com/Homebrew/homebrew/pull/28689#discussion_r11978058
Only deparallelize the *installation* step.

Even though I prefer the declarative flavor of `ENV.deparallelize`, it
threw the baby out with the bathwater by not letting the bootstrapping
process use multiple jobs.

And even though it's really only the *first* `ENV.deparallelize` that
is problematic, I'm replacing both of them for (stylistic?) consistency.
Fix impending = versus == bug.
Run `make` twice *only* when running test suite.