Missing (libffi) dependency for 32 bit MSVC 2017 build

Build completely from scratch (no pkg-config modules)

FAILED: subprojects/glib/gobject/1c9d8d1@@gobject-2.0@sha/gclosure.c.obj
cl @subprojects/glib/gobject/1c9d8d1@@gobject-2.0@sha/gclosure.c.obj.rsp
../subprojects/glib/gobject/gclosure.c(28): fatal error C1083: Cannot open include file: 'ffi.h': No such file or directory