fixed automatic qt-plugins prefix patch

ax_check_qt.m4

@@ -198,7 +198,8 @@ AC_DEFUN([AX_CHECK_QT], [
   if test -n "${MINGW}"; then
     AX_CHECK_VALID_CXX_FLAG([-Wl,-subsystem,windows], [windows console flag])
   fi
-  if test "$prefix" != '/usr' -a "${QT_PLUGIN_PATH}" != "${QT_PLUGIN_PATH#/usr}"; then
+  test "x$prefix" = xNONE && prefix=$ac_default_prefix
+  if test "${QT_PLUGIN_PATH}" = "${QT_PLUGIN_PATH#${prefix}}"; then
     QT_PLUGIN_PATH=${prefix}${QT_PLUGIN_PATH#/usr}
   fi
   AC_ARG_WITH([qt-plugin-path],
@@ -206,6 +207,7 @@ AC_DEFUN([AX_CHECK_QT], [
                               [define a different qt plugin path, current @<:@default=check@:>@])],
               [QT_PLUGIN_PATH=$with_qt_plugin_path],
               [])
+  AC_MSG_NOTICE([Qt Plugins are installed to ${QT_PLUGIN_PATH}])
   AC_SUBST(QTDIR)
   AC_SUBST(QT_PLUGIN_PATH)
   AC_SUBST(CPPFLAGS)