wic: use shutil.which

Use shutil.which to find the executable instead to silence the below warning:
 $ cat tmp/work/intel_x86_64-poky-linux/core-image-base/1.0-r5/temp/log.do_image_wic
 [snip]
 DEBUG: Executing shell function do_image_wic
 /path/layers/oe-core/scripts/wic:27: DeprecationWarning: The distutils package is deprecated and slated for removal in Python 3.12. Use setuptools or check PEP 632 for potential alternatives
  from distutils import spawn
 INFO: Creating image(s)...
 [snip]

[RP: Added conversion for missed function reference]
(From OE-Core rev: 3966cbf5c8a2dbc3a4f0f3eefdbeeb83f522bf87)

Signed-off-by: Mingli Yu <mingli.yu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/wic

@@ -22,9 +22,9 @@ import sys
 import argparse
 import logging
 import subprocess
+import shutil
 
 from collections import namedtuple
-from distutils import spawn
 
 # External modules
 scripts_path = os.path.dirname(os.path.realpath(__file__))
@@ -47,7 +47,7 @@ if os.environ.get('SDKTARGETSYSROOT'):
             break
         sdkroot = os.path.dirname(sdkroot)
 
-bitbake_exe = spawn.find_executable('bitbake')
+bitbake_exe = shutil.which('bitbake')
 if bitbake_exe:
     bitbake_path = scriptpath.add_bitbake_lib_path()
     import bb