Profiles contain RTX symbol (bare metal error)

[0xc0170]

Description

This PR #8887 added debug awareness - linker flag addition keep a section that is RTX specific. This introduced a warning to the baremetal build and mbed 2 - there is no os_cb_sections.

Reading this comment: https://github.com/ARMmbed/mbed-os/pull/8887/files#r243106755 , is this still needed?

One interesting fact about this warning: users think this warning causes build failing in the online compiler. There are so many reports about this, see https://os.mbed.com/questions/85360/Error-Warning-L6320W-ignoring-keep-comma/#answer16979 , https://os.mbed.com/questions/86252/Cant-Compile-Error-Warning-L6320W-Ignori/ and others. The real error there is not always shown, leads a user to believe this warning is actually an error and causing their apps not to build.

Issue request type

[ ] Question
[ ] Enhancement
[X] Bug

[0xc0170]

cc @ARMmbed/mbed-os-core

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-1818

[evedon]

We should be able to work on this shortly as we are looking at changing linker options for bare metal.
cc @rajkan01