Chipyard Makefile -- Enable custom passes for CIRT/FIRRTL?

[Vincent Ulitzsch]

Let's say I compile the BOOM Core with the makefile provided by Chipyard:

cd sims/verilator
make CONFIG=SmallBoomConfig

How can I add custom FIRRTL passes when compiling like this? For example, I would like to add a NestedPrefixModulesAnnotation when compiling the RTL for Boom -- how could I do that when using the Makefile?

Thanks!