!build: forcefully disable DEBUG for ports

[nalajcie]

Description

DEBUG is a common env variable in OSS programs to build unstripped/not-optimized/with-debug-info binaries - we almost never want to do it.

JIRA: CI-494

Motivation and Context

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (refactoring, style fixes, git/CI config, submodule management, no code logic changes)

How Has This Been Tested?

• Already covered by automatic testing.
• New test added: (add PR link here).
• Tested by hand on: (list targets here).

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (list the PRs, preferably in merge-order).
• I will merge this PR by myself when appropriate.

[github-actions]

📝 [shellcheck] _{reported by reviewdog 🐶}
Not following: ./phoenix-rtos-ports/build.subr: openBinaryFile: does not exist (No such file or directory) SC1091

phoenix-rtos-ports/build.sh

Line 77 in efc9853

source "${PREFIX_PROJECT}/phoenix-rtos-ports/build.subr"

[damianloew]

There is an exclamation mark in commit message, I'd prefer to remove it before merge. Except that it's done intentionally (?)

[nalajcie]

There is an exclamation mark in commit message, I'd prefer to remove it before merge. Except that it's done intentionally (?)

We prefix commit message title of breaking changes with ! to easily spot them in git history (commit message body should have info what / how it could break).

[github-actions]

Unit Test Results

7 723 tests  ±0   7 008 ✅ ±0   38m 6s ⏱️ +7s
  443 suites ±0     715 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit efc9853. ± Comparison against base commit 707ec1d.

[damianloew]

There is an exclamation mark in commit message, I'd prefer to remove it before merge. Except that it's done intentionally (?)

We prefix commit message title of breaking changes with ! to easily spot them in git history (commit message body should have info what / how it could break).

Sure, that's the first time I saw this, I will remember for the future