config: Do not prepend definitions with `-D`

[LDong-Arm]

Description

The CMake list MBED_CONFIG_DEFINITIONS in mbed_config.cmake generated by mbed-tools configure has each item prepended with -D. Mbed OS passes this list to target_compile_definitions() which supports macros with or without -D.

Dropping -D from MBED_CONFIG_DEFINITIONS makes the style consistent with MBED_TARGET_DEFINITIONS and makes it easier for a library or application to check if a given macro is on the list.

Test Coverage

• [x] This change is covered by existing or additional automated tests.
• [ ] Manual testing has been performed (and evidence provided) as automated testing was not feasible.
• [ ] Additional tests are not required for this change (e.g. documentation update).

[LDong-Arm]

I can't ever add @ARMmbed/mbed-os-core as a reviewer in this repo. Maybe the team alias needs to be given permission to this repo?

[0xc0170]

The team needs to be collaborator (invite the team to this repo), the team is visible to this repository as reviewers once invited.

[codecov[bot]]

Codecov Report

Merging #299 (57d2e31) into master (57d9e7b) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #299   +/-   ##
=======================================
  Coverage   97.08%   97.08%           
=======================================
  Files          92       92           
  Lines        2782     2782           
=======================================
  Hits         2701     2701           
  Misses         81       81           

[rwalton-arm]

The team needs to be collaborator (invite the team to this repo), the team is visible to this repository as reviewers once invited.

I've added mbed-os-core as a collaborator. Maybe it works now?

[LDong-Arm]

@rwalton-arm Thanks, it works now!