Revert "Remove SIM_OPTS from Makefile"

This reverts commit 014b544: these options are needed for plumbing
Ibex configs through. I've got a follow-up that does this more neatly,
but that depends on some other scripting changes so let's revert the
breakage for now.

dv/uvm/core_ibex/Makefile

@@ -40,6 +40,8 @@ OUT-SEED := $(OUT)/seed-$(SEED)
 export dv_root := $(realpath ../../../vendor/lowrisc_ip/dv)
 export DUT_TOP := dut
 
+# Run time options for ibex RTL simulation
+SIM_OPTS            :=
 # Enable waveform dumping
 WAVES               := 1
 # Enable coverage dump
@@ -153,6 +155,10 @@ endif
 
 include $(sim-cfg-mk)
 
+.PHONY: test-cfg
+test-cfg:
+	@echo "SIM_OPTS" $(SIM_OPTS)
+
 ###############################################################################
 # Utility functions.
 #
@@ -441,7 +447,8 @@ $(rtl-sim-logs): \
 	  --signature-addr $(SIGNATURE_ADDR)       \
 	  --test-dot-seed $(notdir $*)             \
 	  --bin-dir $(OUT-SEED)/instr_gen/asm_test \
-	  --rtl-sim-dir $(OUT-SEED)/rtl_sim
+	  --rtl-sim-dir $(OUT-SEED)/rtl_sim        \
+	  --sim-opts "$(SIM_OPTS)"
 
 .PHONY: rtl_sim_run
 rtl_sim_run: $(rtl-sim-logs)

dv/uvm/core_ibex/scripts/run-rtl.py

@@ -88,6 +88,7 @@ def main() -> int:
     parser.add_argument('--lsf-cmd')
     parser.add_argument('--bin-dir', required=True)
     parser.add_argument('--rtl-sim-dir', required=True)
+    parser.add_argument('--sim-opts')
 
     args = parser.parse_args()
 
@@ -110,6 +111,8 @@ def main() -> int:
     _, base_cmd = get_simulator_cmd(args.simulator, enables)
 
     sim_opts = f'+signature_addr={args.signature_addr}'
+    if args.sim_opts:
+        sim_opts += ' ' + args.sim_opts
 
     # Specialize base_cmd with the right directories and simulator options
     sim_cmd = subst_vars(base_cmd,