Setting `MIMALLOC_SHOW_STATS` to ask mimalloc to print out something
after the process is done is the easiest way to verify that a
mimalloc-enabled Git is running.
So it better work and not try to write to a Win32 Console when it got a
regular file handle instead or, as is the case in Git for Windows'
regular Git Bash window, an emulated pseudo terminal.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>