Cmake comfort

[Ole2mail]

Summary of changes

the change is fixing cmake CMakeLists.txt file generation used by CLion IDE

the change is adding missing TOOLCHAIN path ahead of each compiler tool,
in such case -DTOOLCHAIN_PATH is sufficient in CLion IDE cmake settings to be added.

allowing to build while having neither path nor default toolchain.
the change is fixing improper PRE_LINK command generation.
PRE_LINK command must be using defined CMakeLists.txt variable instead of hardcoded tool name

Impact of changes

only for CLion IDE users

Migration actions required

Documentation

to be added to the CLion doc/readme/howto (if present)

how to specify toolchain path:
"adding -DTOOLCHAIN_PATH is sufficient in CLion IDE cmake settings"

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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)

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Test results

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

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Reviewers

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