[test] fix gcb e2e

[ramonpetgrave64]

Followup to #350

Fixes the tests to correctly edit the payload file, so that this particular test fill fail as expected.

• example-package/.github/workflows/scripts/e2e-verify.common.sh

  Line 540 in e60c8d2

  echo " **** Wrong payload *****"

We may also want to do the same change on the next line, for non-gcb tests

• example-package/.github/workflows/scripts/e2e-verify.common.sh

  Lines 197 to 198 in e60c8d2

  	else
  	jq -c ".payload = \"$(echo "$2" | base64 -w0)\"" <"$1"

Testing

executed the workflow against this PR's branch

https://github.com/slsa-framework/example-package/actions/runs/8756899306/job/24034397658#step:5:150

...
  **** Wrong payload *****
WARNING: Insecure SLSA_VERIFIER_TESTING is enabled.
FAILED: SLSA verification failed: invalid DSSE envelope payload: unexpected end of JSON input
...

[ramonpetgrave64]

@laurentsimon

[laurentsimon]

why do we need to create a file? I think the function needs to print the change, and the caller saves it to file of they want?

[ramonpetgrave64]

ok. something isn't happening correctly here for gcb, then

example-package/.github/workflows/scripts/e2e-verify.common.sh

Lines 540 to 546 in 441e656

	echo " **** Wrong payload *****"
	local bad_prov
	bad_prov="$(mktemp -t slsa-e2e.XXXXXXXX)"
	e2e_set_payload "$PROVENANCE" '{"foo": "bar"}' >"${bad_prov}"
	read -ra badProvenanceArg <<<"$($argr "provenance") ${bad_prov}"
	$verifierCmd "${artifactAndbuilderMinArgs[@]}" "${branchOpts[@]}" "${badProvenanceArg[@]}" "${packageArg[@]}" "${sourceArg[@]}" "github.com/$GITHUB_REPOSITORY"
	e2e_assert_not_eq "$?" "0" "wrong payload"

Like $bad_prov should actually be $PROVENANCE