If supplying weaponry was an aggression in international law, and therefore illegal, wouldn't the whole international arms trade be illegal, by definition? A trade in which Russia is a pretty big participant.
Also, what timeline is this question about? Pre 2014? 2014-2021? From invasion on?
It is unlikely to be considered an aggression to give a weaker country some means to defend itself versus a more powerful aggressor (the term aggressor shouldn't be too controversial when applied from 2014 on). From a purely military viewpoint, the armament range handed out to Ukraine also wouldn't exactly be on the shopping list of a country wanting to attack another.
i.e. Taiwan wouldn't consider itself at risk from massive amounts of Chinese antitank missiles and surface to air missiles, if those were the bulk of PLA weapons. An invasion requires another set of armaments.
Invading Ukraine as a pre-emptive war due to those weapons? Unlikely to be considered as a serious justification given the disparities in GDP, weaponry and armed forces.
Sorry, questions about Russian concerns about NATO admission are on firmer grounds and still don't justify invading.