build failures in mingw64

[Stephen Leake <stephen_leake@stephe-leake.org>]

I'm getting build failures on master (pulled today).

First is:

In file included from C:/Projects/emacs/master/nt/inc/sys/socket.h:82,
                 from thread.h:25,
                 from lisp.h:2261,
                 from dispnew.c:27:
./w32.h:253:10: fatal error: gnutls/gnutls.h: No such file or directory
  253 | #include <gnutls/gnutls.h>
      |          ^~~~~~~~~~~~~~~~~

The file is present in D:/msys64/mingw64/include/gnutls/gnutls.h, but
D:/msys64/mingw64/include is not in the gcc include path. I can work
around that with LIBGNUTLS_CFLAGS="-isystem D:/msys64/mingw64/include".

This appears to be due to a bug in mingw pkgconf; it says:

$ pkgconf --cflags gnutls
-ID:/msys64/mingw64/include/p11-kit-1

but gnutls.h is not in p11-kit-1.


Continuing the make, I get another error:

d:/apps/gnat-gpl_2021/bin/../libexec/gcc/x86_64-w64-mingw32/10.3.1/ld.exe: gnutls.o: in function `gn
utls_try_handshake':
C:\Projects\emacs\master\src/gnutls.c:648: undefined reference to `nanosleep'
C:\Projects\emacs\master\src/gnutls.c:648:(.text+0x49ce): relocation truncated to fit: R_X86_64_PC32
 against undefined symbol `nanosleep'

This is from emacs/src/gnutls.c, which contains "GnuTLS glue for GNU
Emacs". The reference to 'nanosleep' is on line 648; vc-annotate says:

cdbc2f9d274a (Lars Ingebrigtsen           2022-03-04  648)

so I don't see why this only started failing recently. I'll try
bisecting.

I don't have a workaround for this error; trying to add #ifdef on
WindowsNT leads to other errors.

--
-- Stephe