What an interesting discussion. I think perhaps the spelling of Scottish “no” as no’ may be at least partly due to the fact that some Scotsmen, if not all, tend to pronounce adverbial “no” with a glottal stop, rather in the way that “not” is said in Cockney.
But isn’t English “nought” a bit of a sidetrack in the context of this discussion? How close is it, etymologically, to the adverb “not”?  “Nought” or “naught” is a noun, meaning “nothing” (still expressed as “nowt” in parts of Northern England, just as “anything” is expressed as “owt"), though nowadays I believe “naught/nought” is used only to mean “Zero” (my first wife, who grew up in Edinburgh, used to say “nothing” when she meant “zero”: 1-0-3 would be “one-nothing-three").

I suppose you could regard “nought” as a side-track in this discussion, but I added it for the sake of completeness because nought and nocht are related. Dictionary of Scots Language on nocht:

DSL - DOST Nocht, Noucht, Noght, Nought, Noch, Nouch, n. and adv. Also: nochte, noht(t, noct(h, noyht; nowcht; noche, nogh; nowt; noth(t, nothe, nouth(t; noʒt.
[ME. noht, noʒt, noght, nouʒt, nouht, ME. and e.m.E. nought, ME. noh (13th c.), nogh (14 c.), ME. (12–13th c.) and e.m.E. nout, early ME. also nowiht, OE. nóht, nówiht: cf. Naucht adv., No adv.3, and Not adv. and n.]
In certain instances some of the forms exemplified below, esp. nocht, no doubt represent editorial expansions of MS. abbreviated forms, of which not is much the commonest.
Nought, nothing; not.
Where the verb can be either trans. or intrans. and there is no other direct object, it may be uncertain whether nocht is to be taken as the noun (i.e. the direct object) or the adv.: see e.g. 1 (2) below, and examples with verbs such as Avail v. 1 (a), Care v. 1, Cure v.1 2 b, Dow v.1 1, Help v. 3 b, Mak v. 19 a, etc.

The citation shows that 13th century Middle English pronunciation was “noh”.

Interestingly, Alex Salmond, leader of the political party advocating Scottish independence, pronounces “not” with a “T”. Here’s one example - you need only watch about twenty seconds to hear his pronunciation.

edit: I sometimes say “nowt”, though always informally to other northerners.

Thank you, ElizaD.

Louis MacNeice was Irish but that poem has Scottish allusions.

(Bing sings but Walt disnae)