Problem building today's snapshot with MinGW

[Eli Zaretskii]

At Joel's request, I've built today's snapshot of the GDB master
branch using mingw.org's MinGW, and found a problem when running the
produced gdb.exe on versions of Windows older than 8.0 (in my case it
was XP).  The details are described in my report to the Gnulib folks:

  https://lists.gnu.org/archive/html/bug-gnulib/2020-09/index.html

The provisional patch I used to solve this problem is this:

--- gnulib/import/stat-w32.c~	2020-09-10 04:47:11.000000000 +0300
+++ gnulib/import/stat-w32.c	2020-09-10 16:05:46.789125000 +0300
@@ -20,10 +20,14 @@
 
 #if defined _WIN32 && ! defined __CYGWIN__
 
+#if _GL_WINDOWS_STAT_INODES == 2
 /* Ensure that <windows.h> defines FILE_ID_INFO.  */
-#if !defined _WIN32_WINNT || (_WIN32_WINNT < _WIN32_WINNT_WIN8)
-# undef _WIN32_WINNT
-# define _WIN32_WINNT _WIN32_WINNT_WIN8
+# if !defined _WIN32_WINNT || (_WIN32_WINNT < _WIN32_WINNT_WIN8)
+#  undef _WIN32_WINNT
+#  define _WIN32_WINNT _WIN32_WINNT_WIN8
+# endif
+#elif !defined VOLUME_NAME_NONE
+# define VOLUME_NAME_NONE 0x4
 #endif
 
 #include <sys/types.h>