halve CI per-function stack limit to 512KiB

[tersec]

It helped catch

• Regression from 2.0 to version-2-2/devel with refc, LTO and -fstack-usage nim-lang/Nim#24746

so it's worth reducing this further to try to be stricter about catching this category of issues, especially as an eventual migration towards ORC will likely trigger cases here that refc does not.

[tersec]

2025-03-12T08:18:09.3648136Z /github-runner/github-runner-node-02/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-unittest2/unittest2.nim: In function ‘_ZN31runComputeCellsAndKzgProofsTest20runTestX60gensym446_E6string6string’:
2025-03-12T08:18:09.3654243Z /github-runner/github-runner-node-02/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-unittest2/unittest2.nim:1101:15: error: stack usage is 810624 bytes [-Werror=stack-usage=]
2025-03-12T08:18:09.3655806Z  1101 |   proc runTest(suiteName, testName: string): TestStatus {.raises: [], gensym.} =
2025-03-12T08:18:09.3772737Z       |               ^
2025-03-12T08:18:11.5547683Z /github-runner/github-runner-node-02/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-unittest2/unittest2.nim: In function ‘_ZN31runRecoverCellsAndKzgProofsTest20runTestX60gensym628_E6string6string’:
2025-03-12T08:18:11.5552215Z /github-runner/github-runner-node-02/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-unittest2/unittest2.nim:1101:15: error: stack usage is 550864 bytes [-Werror=stack-usage=]
2025-03-12T08:18:17.4333470Z lto1: some warnings being treated as errors
2025-03-12T08:18:17.4747895Z make[2]: *** [/tmp/cc6OF3y9.mk:314: /tmp/ccRnLcUj.ltrans104.ltrans.o] Error 1
2025-03-12T08:18:17.4748638Z make[2]: *** Waiting for unfinished jobs....
2025-03-12T08:19:04.7129896Z /github-runner/github-runner-node-02/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-chronos/chronos/internal/asyncmacro.nim: In function ‘_ZN16readChunkPayload61readChunkPayload__OOZbeacon95chainZsyncZsync95protocol_u17395E3refIN7futures26FutureBasecolonObjectType_EE’:
2025-03-12T08:19:04.7136066Z /github-runner/github-runner-node-02/workspace/nimbus-eth2/nimbus-eth2/vendor/nim-chronos/chronos/internal/asyncmacro.nim:445:15: error: stack usage might be 925216 bytes [-Werror=stack-usage=]
2025-03-12T08:19:04.7137688Z   445 |       iteratorNameSym = genSym(nskIterator, $prcName)
2025-03-12T08:19:04.7138264Z       |               ^
2025-03-12T08:19:06.3545889Z lto1: some warnings being treated as errors
2025-03-12T08:19:06.3856353Z make[2]: *** [/tmp/cc6OF3y9.mk:233: /tmp/ccRnLcUj.ltrans77.ltrans.o] Error 1
2025-03-12T08:20:01.5739374Z lto-wrapper: fatal error: make returned 2 exit status
2025-03-12T08:20:01.5740031Z compilation terminated.
2025-03-12T08:20:01.6689826Z /usr/bin/ld: error: lto-wrapper failed
2025-03-12T08:20:01.6817673Z collect2: error: ld returned 1 exit status
2025-03-12T08:20:01.6843928Z make[1]: *** [nimcache/release/all_tests/all_tests.makefile:3752: build] Error 1

[github-actions]

Unit Test Results

         9 files   -          6    1 578 suites   - 1 052   58m 41s ⏱️ - 19m 28s
  6 339 tests ±         0    5 837 ✔️ ±         0  502 💤 ±    0  0 ❌ ±0 
26 468 runs   - 17 648  25 904 ✔️  - 17 534  564 💤  - 114  0 ❌ ±0 

Results for commit 0450f96. ± Comparison against base commit eec3f17.

♻️ This comment has been updated with latest results.