Problem with macro inside inactive conditional changing autoconf behavior

[Dr. Douglas C. MacKenzie]

I am having trouble with a configure.ac file after upgrading from
libtool 1.5 to 2.2.6 as part of moving from Fedora 10 to Fedora 12.

The file is:

> AC_PREREQ(2.52)
> AC_INIT([testing], [2.0], [testing], [testing])
> AC_CONFIG_MACRO_DIR([m4])
> AM_INIT_AUTOMAKE
> AC_CONFIG_SRCDIR([testing.spec.in])
> 
> dnl --------------------------------------------------------------------------
> 
> AC_ARG_VAR(COMPILER, "Use COMPILER=MSC to compile for WIN32 using Microsoft 
> C++ compiler.\nUse COMPILER=GCC to comnpile using GNU tools (default).\n")
> if test "x$COMPILER" = "xMSC"; then
>    echo "Compiling using Microsoft C++ compiler"
> dnl    AC_LIBTOOL_WIN32_DLL
>     AC_SUBST(BUILD_WINDOWS, true)
> else
>    echo "Compiling using GNU tools"
>    AC_SUBST(AM_CXXFLAGS, "-Wall")
> fi
> AM_CONDITIONAL(BUILD_WINDOWS, test "x$COMPILER" = "xMSC")
> 
> dnl --------------------------------------------------------------------------
> 
> # Checks for programs.
> AC_PROG_CXX
> AC_PROG_CC
> AC_LIBTOOL_DLOPEN
> AC_PROG_LIBTOOL
> AC_CONFIG_FILES([Makefile])
> AC_OUTPUT


The commands:
   autoreconf --force --install
   ./configure
   ./libtool --features

generate:
   host: x86_64-unknown-linux-gnu
   enable shared libraries 
   enable static libraries

But, If I change the "dnl    AC_LIBTOOL_WIN32_DLL" line to   "
AC_LIBTOOL_WIN32_DLL"

The commands:
   autoreconf --force --install
   ./configure
   ./libtool --features

Now generate:
   host: 
   disable shared libraries
   enable static libraries


The package is built both for windows using a cross compiler and for
native linux using gcc.  The test and AM_CONDITIONAL have worked fine up
until the version change.

So, apparently I am misusing the if/fi blocks.

What is the correct way to conditionally include an AC_XXX macro based
on a ./configure command line parameter?

Doug