crt: Fix overflow detection in mingw-w64 _lseeki64() emulation

On recent Windows versions when the current file position does not fit into
the 32 bits then the _lseek() function returns error without setting new
position.

Reflect this behavior in _lseeki64() emulation and fallback to
SetFilePointer() on error.

This fixes t_lseeki64.c test when compiled against msvcrt20.dll and run on
Windows 10 against the system os version of msvcrt20.dll.

mingw-w64-crt/stdio/_lseeki64.c

diff --git a/mingw-w64-crt/stdio/_lseeki64.c b/mingw-w64-crt/stdio/_lseeki64.c
index 747a390..215689b 100644
--- a/mingw-w64-crt/stdio/_lseeki64.c
+++ b/mingw-w64-crt/stdio/_lseeki64.c
@@ -12,7 +12,7 @@
 /* Define 64-bit _lseeki64() function via 32-bit CRT _lseek() function and 64-bit WinAPI SetFilePointer() function */
 __int64 __cdecl _lseeki64(int fd, __int64 offset, int whence)
 {
-  const BOOL offset_overflowed = offset < LONG_MIN || offset > LONG_MAX;
+  BOOL offset_overflowed = offset < LONG_MIN || offset > LONG_MAX;
 
   if (!offset_overflowed)
   {
@@ -21,10 +21,13 @@
      * Just the return value of new offset is truncated to 32 bits.
      * _lseek() does not signal truncation, so check here just for offset
      * overflow for SEEK_SET. For all other cases call SetFilePointer()
-     * to retrieve new 64-bit file offset. */
+     * to retrieve new 64-bit file offset. On recent Windows versions
+     * when the current file position does not fit into the 32 bits then
+     * the _lseek() function returns error without setting new position. */
     errno = 0;
     long ret = _lseek(fd, offset, whence);
-    if (whence == SEEK_SET || (ret == -1 && errno))
+    offset_overflowed = (ret == -1 && errno);
+    if (whence == SEEK_SET && !offset_overflowed)
       return ret;
   }