build: using pymod_do_main in node.gyp

GYP uses the system path when parsing node.gyp;
However, if system python is different from our
gyp runtime python, like '2.7', gyp would crash.

node.gyp

@@ -33,7 +33,7 @@
     # Windows command length limit or there would be an error.
     # See https://docs.microsoft.com/en-us/troubleshoot/windows-client/shell-experience/command-line-string-limitation
     'library_files': [
-      '<!@(python tools/search_files.py --ext js lib)',
+      '<!@pymod_do_main(search_files --ext js lib)',
     ],
     'deps_files': [
       'deps/v8/tools/splaytree.mjs',

tools/gyp_node.py

@@ -7,6 +7,7 @@
 node_root  = os.path.normpath(os.path.join(script_dir, os.pardir))
 
 sys.path.insert(0, os.path.join(node_root, 'tools', 'gyp', 'pylib'))
+sys.path.insert(0, os.path.join(node_root, 'tools', 'search_files'))
 import gyp
 
 # Directory within which we want all generated files (including Makefiles)

tools/search_files.py

@@ -8,15 +8,12 @@
 import argparse
 import utils
 
-def main():
+def DoMain(args = []):
   parser = argparse.ArgumentParser(
     description='Search files with a specific extension under a directory',
     fromfile_prefix_chars='@'
   )
   parser.add_argument('--ext', required=True, help='extension to search for')
   parser.add_argument('directory', help='input directory')
-  options = parser.parse_args()
-  print('\n'.join(utils.SearchFiles(options.directory, options.ext)))
-
-if __name__ == "__main__":
-  main()
+  options = parser.parse_args(args)
+  return '\n'.join(utils.SearchFiles(options.directory, options.ext))