Run chmod as a separate step when building docker image.

[keyurva]

• When building the new services image locally, @kmoscoe ran into an error that said buildkit was required when building this image.
• The only statement in the Dockerfile that requires buildkit is this one where chmod is run as part of COPY.
• Separating it out into its own command gets rid of this requirement so partners don't need to worry about enabling it.
• However, I've still kept it enabled for both manual and auto builds since it turns out that building with buildkit enabled is much faster.
  • The services build takes 11 min with buildkit disabled and 5 min with it enabled.