configure: default to PIE disabled on Windows platforms

If Windows EXE files are built with -pie/-fpie they will fail to
launch. Historically QEMU defaulted to disabling PIE for Windows,
but this setting was accidentally lost when the configure summary
text was removed in

  commit f9332757
  Author: Paolo Bonzini <pbonzini@redhat.com>
  Date:   Mon Feb 3 13:28:38 2020 +0100

    meson: move summary to meson.build

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Fixes: f9332757
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>