Prevent modifying the generated files if generate target fails

If we tried to run make generate and it fails, it will still generate some files and some files not, it will also not run clang-format on the generated files. This will be shown as some of the files are modified while they only have been regenerated without the new additions that we added and without being formatted. We could maybe enhance this by prevent the regeneration of all the files while also report a meaningful error of what happened.

For example: if we tried running make generate without installing third_party/requirements.txt and so a missing dependency , it will report a failure with:

Failed to generate specification.
'bytes' object has no attribute 'read'

Note: This is one of the missing dependencies error, it could also fail with other errors depending on which packages are missing

Start by running make generate and reviewing the generation target, the failure involving third_party/requirements.txt, and the subsequent clang-format step. Trace how partial generated-file changes are left behind; done means a failed generation reports a meaningful error without leaving inconsistent regenerated or unformatted files.