Make improvements for Actually Portable Emacs

- Get SIGWINCH working again on the New Technology
- Correctly handle O_NOFOLLOW in open() on Windows
- Implement synthetic umask() functionality on Windows
- Do a better job managing file execute access on Windows
- Fill in `st_uid` and `st_gid` with username hash on Windows
- Munge UNICODE control pictures into control codes on Windows
- Do a better job ensuring Windows console settings are restored
- Introduce KPRINTF_LOG environment variable to log kprintf to a file

libc/calls/fstat.c

@@ -30,6 +30,10 @@
 /**
  * Returns information about file, via open()'d descriptor.
  *
+ * On Windows, this implementation always sets `st_uid` and `st_gid` to
+ * `getuid()` and `getgid()`. The `st_mode` field is generated based on
+ * the current umask().
+ *
  * @return 0 on success or -1 w/ errno
  * @raise EBADF if `fd` isn't a valid file descriptor
  * @raise EIO if an i/o error happens while reading from file system
@@ -43,14 +47,14 @@ int fstat(int fd, struct stat *st) {
   } else if (__isfdkind(fd, kFdZip)) {
     rc = _weaken(__zipos_fstat)(
         (struct ZiposHandle *)(intptr_t)g_fds.p[fd].handle, st);
-  } else if (!IsWindows() && !IsMetal()) {
+  } else if (IsLinux() || IsXnu() || IsFreebsd() || IsOpenbsd() || IsNetbsd()) {
     rc = sys_fstat(fd, st);
   } else if (IsMetal()) {
     rc = sys_fstat_metal(fd, st);
-  } else if (!__isfdkind(fd, kFdFile)) {
-    rc = ebadf();
-  } else {
+  } else if (IsWindows()) {
     rc = sys_fstat_nt(__getfdhandleactual(fd), st);
+  } else {
+    rc = enosys();
   }
   STRACE("fstat(%d, [%s]) → %d% m", fd, DescribeStat(rc, st), rc);
   return rc;