Don't check for O_CLOEXEC

O_CLOEXEC was introduced in POSIX.2008; we can assume it's
supported on all systems these days.
diff --git a/gio/gdbusauthmechanismsha1.c b/gio/gdbusauthmechanismsha1.c
index 1ed1be6..453c364 100644
--- a/gio/gdbusauthmechanismsha1.c
+++ b/gio/gdbusauthmechanismsha1.c
@@ -37,10 +37,6 @@
 #include "gwin32sid.h"
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#endif
-
 #include "gdbusauthmechanismsha1.h"
 #include "gcredentials.h"
 #include "gdbuserror.h"
diff --git a/gio/gdocumentportal.c b/gio/gdocumentportal.c
index 8d181a5..57fbe4a 100644
--- a/gio/gdocumentportal.c
+++ b/gio/gdocumentportal.c
@@ -33,12 +33,6 @@
 #include "gunixfdlist.h"
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#else
-#define HAVE_O_CLOEXEC 1
-#endif
-
 static gboolean
 get_document_portal (GXdpDocuments **documents,
                      char          **documents_mountpoint,
@@ -167,9 +161,6 @@
             }
           if (fd >= 0)
             {
-#ifndef HAVE_O_CLOEXEC
-              fcntl (fd, F_SETFD, FD_CLOEXEC);
-#endif
               idx = g_unix_fd_list_append (fd_list, fd, NULL);
               close (fd);
             }
diff --git a/gio/glocalfile.c b/gio/glocalfile.c
index 58af717..9c82eef 100644
--- a/gio/glocalfile.c
+++ b/gio/glocalfile.c
@@ -51,10 +51,6 @@
 #define O_BINARY 0
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#endif
-
 #include "gfileattribute.h"
 #include "glocalfile.h"
 #include "glocalfileinfo.h"
diff --git a/gio/glocalfileinfo.c b/gio/glocalfileinfo.c
index eea2668..04e25b7 100644
--- a/gio/glocalfileinfo.c
+++ b/gio/glocalfileinfo.c
@@ -92,10 +92,6 @@
 #endif
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#endif
-
 #include "glocalfileinfo.h"
 #include "gioerror.h"
 #include "gthemedicon.h"
diff --git a/gio/glocalfileoutputstream.c b/gio/glocalfileoutputstream.c
index fda643b..14652bd 100644
--- a/gio/glocalfileoutputstream.c
+++ b/gio/glocalfileoutputstream.c
@@ -65,12 +65,6 @@
 #define O_BINARY 0
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#else
-#define HAVE_O_CLOEXEC 1
-#endif
-
 struct _GLocalFileOutputStreamPrivate {
   char *tmp_filename;
   char *original_filename;
@@ -1315,10 +1309,6 @@
       set_error_from_open_errno (filename, error);
       return NULL;
     }
-#if !defined(HAVE_O_CLOEXEC) && defined(F_SETFD)
-  else
-    fcntl (fd, F_SETFD, FD_CLOEXEC);
-#endif
 
   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
   stream->priv->fd = fd;
diff --git a/gio/gopenuriportal.c b/gio/gopenuriportal.c
index c0e2353..2017c60 100644
--- a/gio/gopenuriportal.c
+++ b/gio/gopenuriportal.c
@@ -33,12 +33,6 @@
 #include "gunixfdlist.h"
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#else
-#define HAVE_O_CLOEXEC 1
-#endif
-
 gboolean
 g_openuri_portal_open_file (GFile       *file,
                             const char  *parent_window,
@@ -90,9 +84,6 @@
           return FALSE;
         }
 
-#ifndef HAVE_O_CLOEXEC
-      fcntl (fd, F_SETFD, FD_CLOEXEC);
-#endif
       fd_list = g_unix_fd_list_new_from_array (&fd, 1);
       fd = -1;
       fd_id = 0;
@@ -363,9 +354,6 @@
           return;
         }
 
-#ifndef HAVE_O_CLOEXEC
-      fcntl (fd, F_SETFD, FD_CLOEXEC);
-#endif
       fd_list = g_unix_fd_list_new_from_array (&fd, 1);
       fd = -1;
       fd_id = 0;
diff --git a/gio/gsubprocess.c b/gio/gsubprocess.c
index dad32da..7b2643b 100644
--- a/gio/gsubprocess.c
+++ b/gio/gsubprocess.c
@@ -115,12 +115,6 @@
 #define O_BINARY 0
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#else
-#define HAVE_O_CLOEXEC 1
-#endif
-
 #define COMMUNICATE_READ_SIZE 4096
 
 /* A GSubprocess can have two possible states: running and not.
@@ -235,10 +229,6 @@
       g_free (display_name);
       /* fall through... */
     }
-#ifndef HAVE_O_CLOEXEC
-  else
-    fcntl (my_fd, F_SETFD, FD_CLOEXEC);
-#endif
 
   return my_fd;
 }
diff --git a/gio/gtrashportal.c b/gio/gtrashportal.c
index 82c1356..5d46d24 100644
--- a/gio/gtrashportal.c
+++ b/gio/gtrashportal.c
@@ -33,12 +33,6 @@
 #include "gunixfdlist.h"
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#else
-#define HAVE_O_CLOEXEC 1
-#endif
-
 #ifndef O_PATH
 #define O_PATH 0
 #endif
@@ -107,10 +101,6 @@
       goto out;
     }
 
-#ifndef HAVE_O_CLOEXEC
-  fcntl (fd, F_SETFD, FD_CLOEXEC);
-#endif
-
   fd_list = g_unix_fd_list_new ();
   fd_in = g_unix_fd_list_append (fd_list, fd, error);
   g_close (fd, NULL);
diff --git a/gio/kqueue/gkqueuefilemonitor.c b/gio/kqueue/gkqueuefilemonitor.c
index b664753..e1d4a7b 100644
--- a/gio/kqueue/gkqueuefilemonitor.c
+++ b/gio/kqueue/gkqueuefilemonitor.c
@@ -32,10 +32,6 @@
 #include <fcntl.h>
 #include <string.h>
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#endif
-
 #include <glib-object.h>
 #include <glib/gfileutils.h>
 #include <gio/gfilemonitor.h>
diff --git a/gio/tests/gsubprocess-testprog.c b/gio/tests/gsubprocess-testprog.c
index b61ccc2..3b19227 100644
--- a/gio/tests/gsubprocess-testprog.c
+++ b/gio/tests/gsubprocess-testprog.c
@@ -124,12 +124,6 @@
   return 0;
 }
 
-#ifdef G_OS_UNIX
-#define GLIB_FD_CLOEXEC "e"
-#else
-#define GLIB_FD_CLOEXEC ""
-#endif
-
 static int
 write_to_fds (int argc, char **argv)
 {
@@ -138,7 +132,7 @@
   for (i = 2; i < argc; i++)
     {
       int fd = atoi (argv[i]);
-      FILE *f = fdopen (fd, "w" GLIB_FD_CLOEXEC);
+      FILE *f = fdopen (fd, "we");
       const char buf[] = "hello world\n";
       size_t bytes_written;
       
@@ -176,7 +170,7 @@
       return 1;
     }
 
-  f = fdopen (fd, "r" GLIB_FD_CLOEXEC);
+  f = fdopen (fd, "re");
   if (f == NULL)
     {
       g_warning ("Failed to open fd %d: %s", fd, g_strerror (errno));
diff --git a/glib/gfileutils.c b/glib/gfileutils.c
index 472be65..e177aaa 100644
--- a/glib/gfileutils.c
+++ b/glib/gfileutils.c
@@ -49,10 +49,6 @@
 #define O_BINARY 0
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#endif
-
 #include "gfileutils.h"
 
 #include "gstdio.h"
diff --git a/glib/giounix.c b/glib/giounix.c
index a5b8605..41c6e27 100644
--- a/glib/giounix.c
+++ b/glib/giounix.c
@@ -44,10 +44,6 @@
 #include <fcntl.h>
 #include <glib/gstdio.h>
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#endif
-
 #include "giochannel.h"
 
 #include "gerror.h"
diff --git a/glib/gkeyfile.c b/glib/gkeyfile.c
index f5b600b..0df69e8 100644
--- a/glib/gkeyfile.c
+++ b/glib/gkeyfile.c
@@ -53,10 +53,6 @@
 
 #endif  /* G_OS_WIN23 */
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#endif
-
 #include "gconvert.h"
 #include "gdataset.h"
 #include "gerror.h"
diff --git a/glib/gmappedfile.c b/glib/gmappedfile.c
index 222e057..80e2e84 100644
--- a/glib/gmappedfile.c
+++ b/glib/gmappedfile.c
@@ -50,10 +50,6 @@
 
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#endif
-
 #include "gconvert.h"
 #include "gerror.h"
 #include "gfileutils.h"
diff --git a/glib/gspawn-posix.c b/glib/gspawn-posix.c
index 8cbf8de..7a00667 100644
--- a/glib/gspawn-posix.c
+++ b/glib/gspawn-posix.c
@@ -111,12 +111,6 @@
 extern char **environ;
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#else
-#define HAVE_O_CLOEXEC 1
-#endif
-
 static gint g_execute (const gchar  *file,
                        gchar       **argv,
                        gchar       **argv_buffer,
@@ -1093,10 +1087,6 @@
       g_assert (read_null != -1);
       parent_close_fds[num_parent_close_fds++] = read_null;
 
-#ifndef HAVE_O_CLOEXEC
-      fcntl (read_null, F_SETFD, FD_CLOEXEC);
-#endif
-
       r = posix_spawn_file_actions_adddup2 (&file_actions, read_null, 0);
       if (r != 0)
         goto out_close_fds;
@@ -1117,10 +1107,6 @@
       g_assert (write_null != -1);
       parent_close_fds[num_parent_close_fds++] = write_null;
 
-#ifndef HAVE_O_CLOEXEC
-      fcntl (write_null, F_SETFD, FD_CLOEXEC);
-#endif
-
       r = posix_spawn_file_actions_adddup2 (&file_actions, write_null, 1);
       if (r != 0)
         goto out_close_fds;
@@ -1141,10 +1127,6 @@
       g_assert (write_null != -1);
       parent_close_fds[num_parent_close_fds++] = write_null;
 
-#ifndef HAVE_O_CLOEXEC
-      fcntl (write_null, F_SETFD, FD_CLOEXEC);
-#endif
-
       r = posix_spawn_file_actions_adddup2 (&file_actions, write_null, 2);
       if (r != 0)
         goto out_close_fds;
diff --git a/gmodule/gmodule.c b/gmodule/gmodule.c
index a6804d3..5b370b7 100644
--- a/gmodule/gmodule.c
+++ b/gmodule/gmodule.c
@@ -51,10 +51,6 @@
 #include <io.h>		/* For open() and close() prototypes. */
 #endif
 
-#ifndef O_CLOEXEC
-#define O_CLOEXEC 0
-#endif
-
 #include "gmoduleconf.h"
 #include "gstdio.h"