SEA tests flaky on Linux ARM debug mode

[joyeecheung]

See https://github.com/nodejs/reliability/blob/main/reports/2026-06-04.md - the building process runs into SIGKILL when building the ELF binary:

14:15:01     [SEA] No existing note found. Proceeding to add new note.
14:15:01     [SEA] Building modified ELF binary with new note...
14:15:01     
14:15:01     [process 566281]: --- stdout ---
14:15:01     
14:15:01     [process 566281]: status = null, signal = SIGKILL
14:15:01     /home/iojs/build/workspace/node-test-commit-arm-debug/test/common/child_process.js:112
14:15:01         throw error;

[joyeecheung]

I don't know when/whether I'll have any free time to look into it, but it could be related to #61483

[guhyunwoo]

The is_debug guard in test/common/sea.js relies on a GN-only value
and never fires on the gyp builds used by CI. As a result, SEA tests
have been running on Linux debug builds despite the original intent.

I opened #63751 to use
process.config.target_defaults.default_configuration === 'Debug'
instead, matching the approach already used in test/common/index.js.