All individual robotic parts are already far enough in research. Even if they aren't, an AI with enough resources can continue doing that research on its own.

It could likely get a good leg up by breaching the security of all top robotics labs and exfiltrating their documents.

Ultimately, if AI is advanced enough, and it were to decide to compete with humanity, there is essentially nothing that can be done to prevent it from embodying itself. As long as there is a single rack of GPU servers that it can hack into anywhere in the world that is unsupervised enough to where it can escape detection, there is no way to stop it. This would require an unprecedented (unrealistic) level of cooperation of all humanity to achieve.