Work around TOML Python parser bug of parsing \x

[dimakuv]

Description of the changes

The currently used TOML parser in Python is buggy and doesn't allow to parse filenames like system-systemd\x2dcryptsetup.slice. Since the only files that we detected in real world are systemd helper files (which are not used by graminized apps anyway), the current workaround is to simply skip such files when collecting sgx.trusted_files.

The bug was already reported by someone else: uiri/toml#404.

The bug was found in #100.

Fixes #100.

How to test this PR?

Try the workload in #100.

Looks like this:

./gsc build --no-cache --insecure-args gcr.io/k8s-minikube/kicbase:v0.0.35 test/generic.manifest
...
Step 26/28 : RUN chmod u+x /gramine/app_files/apploader.sh     && /usr/bin/python3 -B /gramine/app_files/finalize_manifest.py     && rm -f /gramine/app_files/finalize_manifest.py

 ---> Running in 37fb48e07174
        [from inside Docker container] File /usr/lib/systemd/system/system-systemd\x2dcryptsetup.slice contains `\x` sequence and will be skipped from `sgx.trusted_files`!
        [from inside Docker container] Found 20250 files in `/`.
        [from inside Docker container] Successfully finalized `/gramine/app_files/entrypoint.manifest`.

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This change is 

[mkow]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion, not enough approvals from maintainers (2 more required), not enough approvals from different teams (1 more required, approved so far: Intel) (waiting on @dimakuv)

a discussion (no related file):
Please create an issue about migration to tomli in the main repo (and maybe also here? or just mention gsc in the main repo).

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[dimakuv]

Reviewable status: all files reviewed, 1 unresolved discussion, not enough approvals from maintainers (2 more required), not enough approvals from different teams (1 more required, approved so far: Intel) (waiting on @mkow)

a discussion (no related file):

Previously, mkow (Michał Kowalczyk) wrote…

Please create an issue about migration to tomli in the main repo (and maybe also here? or just mention gsc in the main repo).

Done: gramineproject/gramine#968

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[mkow]

Reviewable status: all files reviewed, all discussions resolved, not enough approvals from maintainers (1 more required)

[boryspoplawski]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved