Allowing Native UConv to be built against Windows 32 without a build error.

configure.in

@@ -5075,7 +5075,7 @@ MOZ_ARG_ENABLE_BOOL(native-uconv,
 if test "$MOZ_USE_NATIVE_UCONV"; then
     AC_DEFINE(MOZ_USE_NATIVE_UCONV)
 fi
-if test "$OS_ARCH" != "WINCE" -a "$MOZ_USE_NATIVE_UCONV" -a "$ac_cv_func_iconv" != "yes"; then
+if test "$OS_ARCH" != "WINCE" -a "$OS_ARCH" != "WINNT" -a "$MOZ_USE_NATIVE_UCONV" -a "$ac_cv_func_iconv" != "yes"; then
     AC_MSG_ERROR([iconv() not found.  Cannot enable native uconv support.])
 fi