TFM: Remove ARM Compiler 5 considerations

[hugueskamba]

Summary of changes

ARM Compiler 5 is no longer actively supported and was superseded in
Mbed OS by ARM Compiler 6.

Impact of changes

Breaking change: The binary generated from ARM Compiler 5 cannot be relied on as support has been dropped.

Migration actions required

Use Arm Compiler 6.

Documentation

N/A

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Pull request type

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

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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

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Reviewers

@Patater @evedon

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[ciarmcom]

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

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Test run: FAILED

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• jenkins-ci/mbed-os-ci_greentea-test

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@Patater should confirm but this code comes from another repo so should be fixed there as well although it still might support ARMC5.

[hugueskamba]

@Patater should confirm but this code comes from another repo so should be fixed there as well although it still might support ARMC5.

I did get confirmation from @Patater before making the change that it only needs to be changed in Mbed OS.

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Test run: FAILED

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Failed test jobs:

• jenkins-ci/mbed-os-ci_greentea-test

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[mbed-ci]

Test run: SUCCESS

Summary: 6 of 6 test jobs passed
Build number : 3
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