use exported STRIP to strip binaries

[lukileczo]

Description

• Use exported STRIP to strip binaries
• Fix flag passing in coremark port

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: ia32-generic-qemu

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 update build system to export STRIP variable phoenix-rtos-build#191
• I will merge this PR by myself when appropriate.

[agkaminski]

LGTM

[nalajcie]

maybe add TODO in micropython build.sh to switch to use $STRIP manually?

Other than that, LGTM (CI would fail here, if you have time, you can merge build change, update project and then re-run the CI here (ports are being built only on ports PRs/commits and in nightly campaigns))

[github-actions]

Unit Test Results

7 460 tests  ±0   6 745 ✅ ±0   38m 21s ⏱️ - 2m 45s
  420 suites ±0     715 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit b6df9b0. ± Comparison against base commit be677de.