Linux: (try to) set close-on-exec in open() system call

This Linux-specific extension fixes the close-on-exec race.

src/text/filesystem.c

@@ -110,7 +110,14 @@ int utf8_open (const char *filename, int flags, mode_t mode)
         return -1;
     }
 
-    int fd = open (local_name, flags, mode);
+    int fd;
+
+#ifdef O_CLOEXEC
+    fd = open (local_name, flags | O_CLOEXEC, mode);
+    if (fd == -1 && errno == EINVAL)
+#endif
+    {
+        fd = open (local_name, flags, mode);
 #ifdef HAVE_FCNTL
         if (fd != -1)
         {
@@ -118,6 +125,8 @@ int utf8_open (const char *filename, int flags, mode_t mode)
             fcntl (fd, F_SETFD, FD_CLOEXEC | ((flags != -1) ? flags : 0));
         }
 #endif
+    }
+
     LocaleFree (local_name);
     return fd;
 }