Remote caching does not respect architecture

[jamil-s]

Actual behavior With caching enabled, we have seen arm64 builds fetch artifacts for amd64 architecture builds.

Expected behavior Cache is architecture aware.

To Reproduce Steps to reproduce the behavior:

1. Enable caching using --snapshot-mode=redo --cache=true --customPlatform=linux/amd64 and similarly for --customPlatform=linux/arm64
2. Notice cache hits for different architecture

Triage Notes for the Maintainers

Description	Yes/No
Please check if this a new feature you are proposing	- [ ]
Please check if the build works in docker but not in kaniko	- [ ]
Please check if this error is seen when you use --cache flag	- [ ]
Please check if your dockerfile is a multistage dockerfile	- [ ]