Refactor `mk_def_file()` so that it is usable externally via a new

function ``mk_def_file_internal()`` which is called by a
new ``mk_def_file.py`` script. This will allow other build systems to
generate the ``api_dll.def`` file.

scripts/mk_def_file.py

@@ -0,0 +1,36 @@
+#!/usr/bin/env python
+"""
+Reads a list of Z3 API header files and
+generate a ``.def`` file to define the
+exported symbols of a dll. This file
+can be passed to the ``/DEF`` to the
+linker used by MSVC.
+"""
+import mk_util
+import argparse
+import logging
+import os
+import sys
+
+def main(args):
+  logging.basicConfig(level=logging.INFO)
+  parser = argparse.ArgumentParser(description=__doc__)
+  parser.add_argument("output_file", help="output def file path")
+  parser.add_argument("dllname", help="dllname to use in def file")
+  parser.add_argument("api_files", nargs="+")
+  pargs = parser.parse_args(args)
+
+  for api_file in pargs.api_files:
+    if not os.path.exists(api_file):
+      logging.error('"{}" does not exist'.format(api_file))
+      return 1
+
+  mk_util.mk_def_file_internal(
+    pargs.output_file,
+    pargs.dllname,
+    pargs.api_files)
+  return 0
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv[1:]))
+