Fix asset rebuilds & missing dependencies

[danielrbradley]

Follow-up to #1151

We've restored the .make tracking files and the binaries, but when running make build_[sdk]:

• We depend on .make/build_[sdk]
• Which depends on .make/generate_[sdk]
• Which depends on .make/schema
• Which depends on provider/resources.go and provider/go.mod.

These last two are committed files. The timestamps of the restored .make files are from when the prerequisites job ran, however, the commited source files have a modified timestamp of the point at which they were checked out in the second job, which results in the whole dependency chain above being marked as out of date and being rebuilt. The solution to this is probably to use make --touch instead of assets for resuming makefile builds.

Additionally, this problem should also apply to the bin/$(TFGEN) target, but it doesn't because we're missing a dependency from bin/$(TFGEN) on the source files which can affect it (resources.go and any upstream files).

[danielrbradley]

Fixed by #1157