skip shadow call when euid > 0 on linux

maybe __linux__ is not restrictive enough
and we could consider using a hint sh file
to enable it only on some specific distro?

pp_sys.c

@@ -5436,6 +5436,9 @@ PP(pp_gpwent)
     I32 which = PL_op->op_type;
     SV *sv;
     struct passwd *pwent  = NULL;
+#ifdef __linux__
+    const Uid_t euid = geteuid();
+#endif
     /*
      * We currently support only the SysV getsp* shadow password interface.
      * The interface is declared in <shadow.h> and often one needs to link
@@ -5562,7 +5565,11 @@ PP(pp_gpwent)
 	 * --jhi */
 	/* Some AIX setups falsely(?) detect some getspnam(), which
 	 * has a different API than the Solaris/IRIX one. */
+
 #   if defined(HAS_GETSPNAM) && !defined(_AIX)
+#      ifdef __linux__
+    if (!PerlProc_geteuid())
+#      endif
 	{
 	    dSAVE_ERRNO;
 	    const struct spwd * const spwent = getspnam(pwent->pw_name);