[Ping] Port of VTV for Cygwin and MinGW

[Jakub Jelinek]

On Thu, Jan 29, 2015 at 10:28:17AM -0800, H.J. Lu wrote:
> >> --- acinclude.m4        (revision 220257)
> >> +++ acinclude.m4        (working copy)
> >> @@ -2320,8 +2320,6 @@
> >>    AC_MSG_CHECKING([for vtable verify support])
> >>    AC_MSG_RESULT([$enable_vtable_verify])
> >>
> >> -  AM_CONDITIONAL(VTV_CYGMIN, test $vtv_cygmin = yes)
> >> -
> >>    if test $enable_vtable_verify = yes; then
> >>      case ${target_os} in
> >>        cygwin*|mingw32*)
> >> @@ -2341,6 +2339,8 @@
> >>      VTV_CXXLINKFLAGS=
> >>    fi
> >>
> >> +  AM_CONDITIONAL(VTV_CYGMIN, test $vtv_cygmin = yes)
> >> +
> >
> 
> Or we can just do
> 
> AM_CONDITIONAL(VTV_CYGMIN, test x$vtv_cygmin = xyes)

Or that, but that is not what you've checked in.
Some shells will be upset about test $vtv_cygmin = yes when
$vtv_cygmin expands to empty string.

	Jakub