chore(cannon): migrate testdata Makefiles to justfiles

[ajsutton]

Summary

• Migrates cannon/testdata/, cannon/testdata/go-1-24/, and cannon/testdata/go-1-25/ Makefiles to justfiles
• The Make pattern rules (bin/%.64.elf) for building ELF binaries from go.mod directories are replaced with shell loops that discover and build all directories dynamically
• Updates cannon/justfile to call just instead of make -C for testdata targets
• Updates CircleCI to use just elf instead of make elf

Stack

1. optimism#19473 — linter migration + shared infrastructure
2. optimism#19474 — cannon migration
3. optimism#19475 — op-e2e migration
4. optimism#19476 — op-program migration
5. optimism#19477 — root Makefile migration
6. optimism#19482 — CI config update
7. This PR — cannon testdata migration

Test plan

• just elf in cannon/testdata/ builds all ELF binaries
• just elf in cannon/testdata/go-1-24/ builds go-1-24 ELF binaries
• CI cannon tests pass

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.7%. Comparing base (9a50c60) to head (8e9e604).
⚠️ Report is 3 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #19483      +/-   ##
===========================================
+ Coverage     75.3%    75.7%    +0.4%     
===========================================
  Files          194      671     +477     
  Lines        11285    71270   +59985     
===========================================
+ Hits          8502    54017   +45515     
- Misses        2639    17109   +14470     
  Partials       144      144              

Flag	Coverage Δ
cannon-go-tests-64	66.4% <ø> (ø)
contracts-bedrock-tests	80.2% <ø> (ø)
unit	75.8% <ø> (?)

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see 477 files with indirect coverage changes

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[sebastianst]

Review: cannon testdata Makefiles → justfiles

Small, clean migration. The Make pattern rules are replaced with shell loops that discover and build ELFs dynamically. A few notes:

1. Lost parallel builds

The original Make pattern rules (bin/%.64.elf) could build all ELF binaries in parallel with make -j. The just version uses a sequential for mod in */go.mod loop. For testdata binaries this probably doesn't matter much, but worth noting.

2. dump target changed discovery mechanism

Original: $(patsubst %/go.mod,bin/%.dump,$(wildcard */go.mod)) — dumps only ELFs that correspond to */go.mod directories.
New: for elf in bin/*.64.elf — dumps any .64.elf in bin/, regardless of whether a matching go.mod exists.

Unlikely to matter in practice (stale ELFs in bin/ would be an unusual scenario), but it's a subtle behavioral difference.

3. dump lost a TODO comment

Original had # TODO: currently have the little-endian toolchain, but should use the big-endian one. The -EB compat flag works though. — dropped from the justfile.

Everything else looks good

• elf64: elf reverses the dependency direction from the original (elf: elf64) but produces the same result — elf does the work, elf64 is an alias
• clean correctly adds || true to handle missing bin/ directory (needed since just fails on non-zero exit, unlike Make with @)
• cannon/justfile correctly updated from make -C to just ./testdata/elf syntax
• CircleCI change is straightforward make elf → just elf
• Deprecated shim order puts elf first, so bare make (no target) still defaults to building ELFs

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Review generated by Claude Code

[sebastianst]

Follow-up: recovering lost parallelism

A few patterns to recover the make -j parallelism where it matters:

ELF build loops — replace the sequential for with parallel:

mkdir -p bin
parallel --tag 'cd {} && GOOS=linux GOARCH=mips64 GOMIPS64=softfloat go build -o "../bin/{}.64.elf" .' ::: $(ls -d */go.mod | xargs -n1 dirname)

Recipe-level deps (e.g. reproducible-prestate) — just always runs deps sequentially, but you can parallelize in the recipe body with & + wait:

[script('bash')]
reproducible-prestate:
    set -euo pipefail
    make -C ./op-program build-reproducible-prestate &
    (cd rust && just build-kona-reproducible-prestate) &
    wait
    make -C ./op-program output-prestate-hash
    cd rust && just output-kona-prestate-hash

There's already a MAP_JUST variable in justfiles/default.just that wires up GNU parallel for just targets — it's just not used anywhere yet.

That said, parallel is a heavier dependency than make -j. For testdata ELFs it's probably not worth it. The reproducible-prestate case (two Docker builds) is where it matters most, and & + wait is simple enough.

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Comment generated by Claude Code