Make improvements

- Introduce ualarm() function
- Make rename() report EISEMPTY on Windows
- Always raise EINVAL upon open(O_RDONLY|O_TRUNC)
- Add macro so ./configure will detect SOCK_CLOEXEC
- Fix O_TRUNC without O_CREAT not working on Windows
- Let fcntl(F_SETFL) change O_APPEND status on Windows
- Make sure pwrite() / pread() report ESPIPE on sockets
- Raise ESPIPE on Windows when pwrite() is used on pipe
- Properly compute O_APPEND CreateFile() flags on Windows
- Don't require O_DIRECTORY to open directories on Windows
- Fix more instances of Windows reporting EISDIR and ENOTDIR
- Normalize EFTYPE and EMLINK to ELOOP on NetBSD and FreeBSD
- Make unlink() / rmdir() work on read-only files on Windows
- Validate UTF-8 on Windows paths to fix bug with overlong NUL
- Always print signal name to stderr when crashing due to SIG_DFL
- Fix Windows bug where denormalized paths >260 chars didn't work
- Block signals on BSDs when thread exits before trashing its own stack

libc/calls/pwritev.c

@@ -54,7 +54,11 @@ static ssize_t Pwritev(int fd, const struct iovec *iov, int iovlen,
 
   if (IsWindows()) {
     if (fd < g_fds.n) {
-      return sys_write_nt(fd, iov, iovlen, off);
+      if (g_fds.p[fd].kind == kFdSocket) {
+        return espipe();
+      } else {
+        return sys_write_nt(fd, iov, iovlen, off);
+      }
     } else {
       return ebadf();
     }