Pass toolchain's root into ExternalProject

[Ignition]

Description

With the new toolchain-v5 there was an issue where 3rd party lib was being built with incorrect libzstd on some developers machines. This causes linking issues.

Fix is to provide the toolchain's root via CMAKE_PREFIX_PATH in our usage of ExternalProject_Add.

Our toolchain environment file can be updated to introduce MG_TOOLCHAIN_ROOT to make this work.

@MarkoBarisic @gitbuda should we republish toolchain-v5 to have MG_TOOLCHAIN_ROOT?

[master < Task] PR

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  • "Pass toolchain's root into ExternalProject"

Documentation checklist

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[gitbuda]

Nice!
@mathstuf thanks a lot for your contribution!
@MarkoBarisic, yes, we should extend the activate script by adding MG_TOOLCHAIN_ROOT 👀

[sonarcloud]

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