Provide subsets for AltJits for RISC-V and LoongArch64

[MichalPetryka]

Currently, there's no way to test JIT output for RISC-V and LoongArch64 without using hardware based on them, as such it'd be useful to have AltJits for them available in order to be able to verify JIT codegen on them after changes.
Since those platforms aren't officially supported, they should be under separate opt-in build subsets.

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Issue Details

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Currently, there's no way to test JIT output for RISC-V and LoongArch64 without using hardware based on them, as such it'd be useful to have AltJits for them available in order to be able to verify JIT codegen on them after changes.
Since those platforms aren't officially supported, they should be under separate opt-in build subsets.

Author:	MichalPetryka
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[am11]

If the existing Clr.AllJits subset cannot support the community platforms without making it optional, something like Clr.AltJitsCommunity would do the trick (and maybe rename Clr.AllJits to keep these aspects scalable).

[hez2010]

I think it's fine to build all jits available in Clr.AllJits as it can help verify whether a change would break the community platforms or not with the existing CI setup.