[newlib-cygwin] Cygwin: restore one more '#ifdef __x86_64__'

[Ken Brown]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=ddce45112d96d35d57c8423747d615f86f5e5c09

commit ddce45112d96d35d57c8423747d615f86f5e5c09
Author: Ken Brown <kbrown@cornell.edu>
Date:   Sat Jun 11 08:56:08 2022 -0400

    Cygwin: restore one more '#ifdef __x86_64__'

Diff:
---
 winsup/cygwin/dcrt0.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc
index a8ed8e2fe..9cbb8908f 100644
--- a/winsup/cygwin/dcrt0.cc
+++ b/winsup/cygwin/dcrt0.cc
@@ -1016,6 +1016,7 @@ __cygwin_exit_return:			\n\
 extern "C" void __stdcall
 _dll_crt0 ()
 {
+#ifdef __x86_64__
   /* Starting with Windows 10 rel 1511, the main stack of an application is
      not reproducible if a 64 bit process has been started from a 32 bit
      process.  Given that we have enough virtual address space on 64 bit
@@ -1048,6 +1049,9 @@ _dll_crt0 ()
       else
 	fork_info->alloc_stack ();
     }
+#else
+#error unimplemented for this target
+#endif
 
   fesetenv (FE_DFL_ENV);
   _main_tls = &_my_tls;