We already attest to the relevant dist-archive in inputs.SHA256SUMS,
which is recorded at build-time.
We use a SKIPATTEST.TAG file to indicate output directories which do not
require attestation (much like the CACHEDIR.TAG specification).
Generally, it's better to have build scripts declare properties of
directories instead of introducing name-based special cases in attest
scripts since build scripts have a more detailed context of what is
going on.
At build/codesigning-time, hash build inputs and output the digest to
${OUTDIR}/inputs.SHA256SUMS, which gets included in the final SHA256SUMS
constructed by guix-attest.
Example final SHA256SUMS:
ee832d2a35b7701bff581dea05a536118b118e3ad0a587a2855b6ee8cd6fba20 inputs/bitcoin-78199266af7b.tar.gz
ca765e70a0c12866dd63c0be228b675278a26329e5f8f5b5c52fd09200fedf21 bitcoin-78199266af7b-powerpc64le-linux-gnu-debug.tar.gz
dae95327d7f2c324e2728c4b73627be6cb2c0d2f2e5bea940d1d5e6463939327 bitcoin-78199266af7b-powerpc64le-linux-gnu.tar.gz
