[nrf fromtree] scripts: west: nrfutil: Use build dir to store generated json

Until now the code was using the path to the .hex file to select the
directory where the generated JSON file required for nrfutil would be
generated. But this has a problem: if the .hex file in a sysbuild
project is located in the tree as a precompiled binary, the runner would
place a file in there and make the tree dirty. Instead use the build_dir
folder which always corresponds (in both sysbuild and regular builds)
to the current target build directory.

Signed-off-by: Carles Cufi <[email protected]>
(cherry picked from commit d6f5aa9)

Author: carlescufi

scripts/west_commands/runners/nrfutil.py

@@ -152,7 +152,7 @@ def _append_batch(self, op, json_file):
 
     def _exec_batch(self):
         # Use x-append-batch to get the JSON from nrfutil itself
-        json_file = Path(self.hex_).parent / 'generated_nrfutil_batch.json'
+        json_file = Path(self.cfg.build_dir) / 'zephyr' / 'generated_nrfutil_batch.json'
         json_file.unlink(missing_ok=True)
         for op in self._ops:
             self._append_batch(op, json_file)