发布：
http://blog.qt.io/blog/2017/01/23/qt-5-8-released/
说法一：Qt Lite” is not a tool, but a concept that enables you to opt out of unwanted features more easily (or at all).
There is also a graphical convenience tool for selecting such feature sets, which is currently part of the “Qt for Device Creation” offering. On the command line, you can use configure’s “-feature-*” and “-no-feature-*” options.
说法二：Qt Lite is a term which refers to the enhancements that were made to the existing (Open Source) Qt configure functionality in Qt 5.8. You implicitly use Qt Lite any time you run the configure script, without even knowing it. Essentially, all “Qt Lite” does is provide a lot more of those -feature-* / -no-feature-* flags to configure than were previously available, and makes sure they actually work in concert with each other. Very significant internal changes were made to provide a scalable infrastructure for doing this.
The part which is available only under Qt for Device Creation licenses is the Qt Lite graphical configuration tool. The graphical tool is not required to use Qt Lite, but makes the process significantly easier by providing you with an easy-to-use interface for configuring features and automatically generating the configure.json files which are tedious and difficult to write by hand.
Hopefully this clarifies the situation for you.
最早的说明：
http://blog.qt.io/blog/2016/08/18/introducing-the-qt-lite-project-qt-for-any-platform-any-thing-any-size/
工具：
http://doc.qt.io/QtEnterpriseEmbedded/qt-configuration-tool.html
看起来免费版是没有这个功能的。
仔细研究了下，是增加了很多宏
具体 在：
Srcqtbasesrccorelibglobalqfeatures.txt
比如说里面的FTP的特性，如果你不想要，就增加
#define QT_NO_FTP 1
这样应该就可以了。5.7.1里有个qconfig工具，直接用那个也可以生成一个头文件。
经过指点得知，我发现的这个功能早就有了...
http://www.qtcn.org/bbs/read-htm-tid-62495.html