bug#37852: Build failure on MSYS2 (undefined reference to _chk functions)

[Eli Zaretskii]

> From: Richard Copley <rcopley@gmail.com>
> Date: Mon, 21 Oct 2019 13:28:29 +0100
> 
> Linking auxiliary executables fails with undefined references to 
> (FORTIFY_SOURCE?) functions 
> __memcpy_chk and __memmove_chk. This is apparently caused by some change in 
> MSYS2, because
> previously buildable commits now fail. Transcript below.

Looks like FORTIFY_SOURCE requires linking against -lssp?  Can you try
adding that, e.g. by

  make LIBS_SYSTEM=-lssp