test(vt): drop the cmp dependency from the release-notes contract

Wiring this contract into scripts/test.sh Step 0l made it run on the Windows VM
for the first time, where it failed with 'cmp: command not found' -- MSYS2 does
not ship cmp, and diff is not guaranteed either. The script already requires
python3, so compare the bytes there instead.

The failure was real coverage working as intended: the contract had never run on
Windows before, because it was registered only in the test.sh version that this
branch replaces.

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

Author: DeusData

tests/test_vt_release_notes_contract.sh

@@ -118,7 +118,10 @@ done
 ! grep -q '70+' "$FIX/first.md" || fail "unmeasured engine claim returned"
 
 run_notes "$FIX/first.md" "$FIX/second.md"
-cmp -s "$FIX/first.md" "$FIX/second.md" || fail "marked release-note update is not idempotent"
+# python3 rather than cmp/diff: this contract runs on the Windows VM's MSYS2
+# shell too, where neither is guaranteed to be on PATH (cmp is not).
+python3 -c 'import sys;sys.exit(0 if open(sys.argv[1],"rb").read()==open(sys.argv[2],"rb").read() else 1)' \
+  "$FIX/first.md" "$FIX/second.md" || fail "marked release-note update is not idempotent"
 
 cp "$FIX/binaries/vt-results.tsv" "$FIX/binaries/vt-results.clean.tsv"
 printf '\textra-cell\n' >> "$FIX/binaries/vt-results.tsv"