repo: use explicit Python executable to run main.py

Small step to support non-POSIX platforms.

Change-Id: I3bdb9c82c2dfbacb1da328caaa1a406ab91ad675

repo

@@ -719,7 +719,7 @@ def main(orig_args):
     repo_main = my_main
 
   ver_str = '.'.join(map(str, VERSION))
-  me = [repo_main,
+  me = [sys.executable, repo_main,
         '--repo-dir=%s' % rel_repo_dir,
         '--wrapper-version=%s' % ver_str,
         '--wrapper-path=%s' % wrapper_path,
@@ -727,7 +727,7 @@ def main(orig_args):
   me.extend(orig_args)
   me.extend(extra_args)
   try:
-    os.execv(repo_main, me)
+    os.execv(sys.executable, me)
   except OSError as e:
     print("fatal: unable to start %s" % repo_main, file=sys.stderr)
     print("fatal: %s" % e, file=sys.stderr)