Add additional steps in gcc validation leg

[am11]

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Issue Details

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Author:	am11
Assignees:	-
Labels:	area-Infrastructure-coreclr, community-contribution
Milestone:	-

[am11]

cc @safern, @akoeplinger, @lambdageek, perhaps this hybrid approach is not elegant in terms of code; placing non-coreclr steps in coreclr/templates/build-job.yml, but this is the minimal change to append a few "native" steps to the existing build validation leg (which was added to protect the build with GNU toolchain). Note that we do not publish artifacts anywhere from this leg.

[jkoritzinsky]

@am11 since the compiler support is wired up through the root build script, I’d suggest using the global-build-job template instead and pass in a subset argument for all the native subsets and the property to set the native compiler. That will probably be much easier to maintain over time.

[am11]

I am keeping the step in coreclr script for now as it is a minimal change. We have similar steps in that file.

That will probably be much easier to maintain over time.

Probably, but lets do the refactoring in a separate PR.

[safern]

I think we should use the global-build-job template as @jkoritzinsky suggested, it will be cleaner and easier to maintain long term.