test: modify file_truncate for win32 build
test: modify file_truncate for win32 build

Truncate using file descriptor and use _chsize_s to truncate on win32

xunchangguo/BMX,xunchangguo/BMX,Limecraft/ebu-bmx,Limecraft/ebu-bmx,stuarthicks/bmx,stuarthicks/bmx,xunchangguo/BMX,kierank/bmxlib-bmx,Limecraft/ebu-bmx,kierank/bmxlib-bmx,stuarthicks/bmx,kierank/bmxlib-bmx