Move pre-build tidyup into Python for build-instr-gen.py

dv/uvm/core_ibex/Makefile

@@ -276,7 +276,6 @@ risc-dv-files := $(shell find $(GEN_DIR) -type f)
 $(metadata)/.instr_gen.build.stamp: \
   $(instr-gen-build-vars-prereq) \
   $(risc-dv-files) scripts/build-instr-gen.py | $(metadata)
-	$(verb)rm -rf $(OUT-SEED)/instr_gen
 	$(verb)scripts/build-instr-gen.py        \
 	  $(verb-arg)                            \
 	  --simulator $(SIMULATOR)               \

dv/uvm/core_ibex/scripts/build-instr-gen.py

@@ -5,6 +5,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 import argparse
+import shutil
 import sys
 
 from scripts_lib import run_one, start_riscv_dv_run_cmd
@@ -20,6 +21,12 @@ def main() -> int:
 
     args = parser.parse_args()
 
+    # Delete the output directory if it existed to ensure a clear build
+    try:
+        shutil.rmtree(args.output)
+    except FileNotFoundError:
+        pass
+
     cmd = (start_riscv_dv_run_cmd(args.verbose) +
            ['--co', '--steps=gen',
             '--simulator', args.simulator,