Run RemoveValidIf pass for updated CIRCT

[abejgonzalez]

Adds an extra flag that allows the compiler to run extra LowFirrtl passes needed for CIRCT to pass (i.e. run the RemoveValidIf pass).

[abejgonzalez]

Another way to do this is to add a RunFirrtlTransformAnnotation to the .json that we emit in CY that specifies the xform to run (i.e. the ExtraPassesTransform). That will avoid us having to add an extra compiler flag that is redundant.

IMO this is cleaner

[joonho3020]

I agree that having duplicate compile flags isn't clean. Are we only performing the ExtraPassesTransform when only using the ENABLE_CUSTOM_FIRRTL_PASS flag?

[abejgonzalez]

I agree that having duplicate compile flags isn't clean. Are we only performing the ExtraPassesTransform when only using the ENABLE_CUSTOM_FIRRTL_PASS flag?

Correct. We are only running this when dumping out LowFIRRTL because CIRCT no longer supports validif statements (which are emitted in SFC LowFIRRTL)

[joonho3020]

I see. I can try deduplicating this flag later. In the meanwhile, we can also just merge this in.

[abejgonzalez]

Let's merge this in when the new-hammer work gets merged in.

[joonho3020]

okey-dokey

[harrisonliew]

Verified that this works. Can we merge this for ucb-bar/chipyard#1324?