The phrase "supply chain attack" makes it sound like it's some big, hard to avoid problem. But almost always, it's just developer negligence:

1. Developer allows some organization to inject arbitrary code in the developer's system

2. Organization injects malicious code

3. Developer acts all surprised and calls it an "attack"

Maybe don't trust 3rd parties so much? There's technical means to avoid it.

Calling this situation a supply chain attack is like saying you were victim of a "ethanol consumption attack" when you get drunk from drinking too many beers.