CMake: Correct ARM toolchain MCU core flags

[hugueskamba]

Summary of changes

Some armasm flags are passed to the ASM whilst we actually use armclang to invoke it. This causes build failures as armclang is not compatible with armasm flags.
This commit passes the same flags to all tools in the chain.

Impact of changes

Migration actions required

Documentation

---

Pull request type

[x] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

---

Test results

[] No Tests required for this change (E.g docs only update)
[x] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

---

Reviewers

---

[ciarmcom]

@hugueskamba, thank you for your changes.
@ARMmbed/mbed-os-tools @ARMmbed/mbed-os-maintainers please review.

[mbed-ci]

Jenkins CI Test : ❌ FAILED

Build Number: 1 | 🔒 Jenkins CI Job | 🌐 Logs & Artifacts

CLICK for Detailed Summary

jobs	Status
jenkins-ci/mbed-os-ci_unittests	✔️
jenkins-ci/mbed-os-ci_cmake-example-ARM	✔️
jenkins-ci/mbed-os-ci_cmake-example-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_build-greentea-ARM	✔️
jenkins-ci/mbed-os-ci_build-example-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_build-cloud-example-ARM	❌
jenkins-ci/mbed-os-ci_build-example-ARM	✔️
jenkins-ci/mbed-os-ci_build-greentea-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_build-cloud-example-GCC_ARM	✔️

[0xc0170]

Restarted

[mbed-ci]

Jenkins CI Test : ✔️ SUCCESS

Build Number: 2 | 🔒 Jenkins CI Job | 🌐 Logs & Artifacts

CLICK for Detailed Summary

jobs	Status
jenkins-ci/mbed-os-ci_cmake-example-ARM	✔️
jenkins-ci/mbed-os-ci_unittests	✔️
jenkins-ci/mbed-os-ci_cmake-example-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_build-greentea-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_build-greentea-ARM	✔️
jenkins-ci/mbed-os-ci_build-example-ARM	✔️
jenkins-ci/mbed-os-ci_build-cloud-example-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_build-example-GCC_ARM	✔️
jenkins-ci/mbed-os-ci_build-cloud-example-ARM	✔️
jenkins-ci/mbed-os-ci_cmake-example-test	✔️
jenkins-ci/mbed-os-ci_greentea-test	✔️