在realvnc下载了源码版本3.3.7进行交叉编译，解压源码后查看README分两步进行编译，其编译方式说明为：
To build this distribution you need a C++ compiler as well as a C compiler.
You also need a reasonably recent version of the X window system installed.
This come as standard with most unix machines. If you don't have it installed,
see http://www.x.org or http://www.xfree86.org
To build everything but Xvnc, do:
% ./configure
% make
This should build first some libraries - zlib, rdr and rfb - then vncconnect,
vncpasswd and vncviewer. If you already have zlib installed on your system you
can run "./configure --with-installed-zlib" if you prefer (this is strongly
advised on FreeBSD, since we've been told there are problems otherwise).
Xvnc differs from the other programs in that it is built inside a cut-down
version of the X build tree. This is based around the XFree86 3.3.2 "server
only" distribution, which in turn is based on the X11R6.3 distribution from
the X consortium. To build Xvnc, do:
% cd Xvnc
% make World
我要实现交叉编译源码在第一步方式中可以设置configure参数实现交叉编译，编译通过；第二步进去Xvnc目录下只有Makefile相关文件，而没有configure文件无法配置交叉编译，于是考虑修改Makefile文件来交叉编译，可是在它的每个子目录下都有一个Makefile不能修改每一个！请高手帮忙：在没有configure文件而且主目录和子目录都有Makefile下怎么实现交叉编译，如果直接make World将直接gcc编译了而非cross-compile！不知道怎么实现，还请多多帮忙解决，谢谢！
