[dvsim/verilator] Fix pre-build cmd failure when hw/foundry is absent
[dvsim/verilator] Fix pre-build cmd failure when hw/foundry is absent

Signed-off-by: Michael Schaffner <a005a2d3342a687ea2d05360c953107acbe83e08@opentitan.org>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan