win32: return an error when lseek is applied to a pipe

tail failed to process input from a pipe correctly:

   $ echo -n 54321 | tail -c 3
   543

It was trying to use lseek as an optimisation but WIN32 lseek doesn't
return an error whan applied to a pipe.  Fix this by providing a wrapper
for lseek.

1 files changed, 14 insertions, 0 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index ebdcdee26..23ca5d3dd 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -1030,3 +1030,17 @@ DIR *mingw_opendir(const char *path)
 
         return opendir(path);
 }
+
+off_t mingw_lseek(int fd, off_t offset, int whence)
+{
+        HANDLE h = (HANDLE)_get_osfhandle(fd);
+        if (h == INVALID_HANDLE_VALUE) {
+                errno = EBADF;
+                return -1;
+        }
+        if (GetFileType(h) != FILE_TYPE_DISK) {
+                errno = ESPIPE;
+                return -1;
+        }
+        return _lseeki64(fd, offset, whence);
+}