[newlib-cygwin] Cygwin: pty: Change how to determine if running as service or not.

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=e5db0d2fe06d66607f7d3423f75451fab2bda6ee

commit e5db0d2fe06d66607f7d3423f75451fab2bda6ee
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date:   Wed Nov 6 21:08:43 2019 +0900

    Cygwin: pty: Change how to determine if running as service or not.

Diff:
---
 winsup/cygwin/fhandler_tty.cc | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index da6119d..0109d45 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -3094,22 +3094,11 @@ pty_master_fwd_thread (VOID *arg)
    the helper process is running as privileged user while
    slave process is not. This function is used to determine
    if the process is running as a srvice or not. */
-static bool
+inline static bool
 is_running_as_service (void)
 {
-  DWORD dwSize = 0;
-  PTOKEN_GROUPS pGroupInfo;
-  tmp_pathbuf tp;
-  pGroupInfo = (PTOKEN_GROUPS) tp.w_get ();
-  NtQueryInformationToken (hProcToken, TokenGroups, pGroupInfo,
-					2 * NT_MAX_PATH, &dwSize);
-  for (DWORD i=0; i<pGroupInfo->GroupCount; i++)
-    if (RtlEqualSid (well_known_service_sid, pGroupInfo->Groups[i].Sid))
-      return true;
-  for (DWORD i=0; i<pGroupInfo->GroupCount; i++)
-    if (RtlEqualSid (well_known_interactive_sid, pGroupInfo->Groups[i].Sid))
-      return false;
-  return true;
+  return check_token_membership (well_known_service_sid)
+    || cygheap->user.saved_sid () == well_known_system_sid;
 }
 
 bool