bug#65339: build failure on Android (Termux)

[Eli Zaretskii]

> From: Bruno Haible <bruno@clisp.org>
> Date: Wed, 16 Aug 2023 12:25:21 +0200
> 
> fdsan: attempted to close file descriptor 2, expected to be unowned, actually 
> owned by FILE* 0xb678438c
> make[2]: *** [Makefile:1012: bootstrap-emacs.pdmp] Aborted
> make[2]: *** Deleting file 'bootstrap-emacs.pdmp'
> make[2]: Leaving directory '/data/data/com.termux/files/home/emacs/src'
> make[1]: *** [Makefile:554: src] Error 2
> make[1]: Leaving directory '/data/data/com.termux/files/home/emacs'
> make[1]: Entering directory '/data/data/com.termux/files/home/emacs'
> ***
> *** "make all" failed with exit status 2.
> 
> The line "fdsan: attempted to close file descriptor 2, expected to be unowned"
> is apparently emitted by Android's "file descriptor sanitizer".
> 
> There's a discussion of this message here:
> https://github.com/termux/termux-packages/issues/6592
> and a workaround patch has been posted here:
> https://github.com/termux/termux-packages/blob/master/packages/emacs/disable-fdsan.patch
> 
> With this workaround patch, the build gets much further: It produces a
> working 'src/emacs' executable.
> 
> Would it be possible to
>   - either change Emacs' FILE / dirfd handling so that it no longer produces
>     this fdsan alert,
>   - or include the workaround patch in Emacs upstream?

What is problematic with our FILE / dirfd handling that causes wrath
on the part of the Android gods?