trunk:src/doc minor doc update about compilation

git-svn-id: https://svn.code.sf.net/p/kaldi/code/trunk@3243 5e6a8d80-dfce-4ca6-a32a-6e07a63d50c8

src/doc/build_setup.dox

@@ -144,6 +144,7 @@ preprocessor variables, setting compile options, linking with libraries, and so
 \section build_setup_platforms Which platforms has Kaldi been compiled on?
 
 We have compiled Kaldi on Windows, Cygwin, various flavors of Linux (including
-Ubuntu, CentOS, Debian and SUSE), and Darwin.
+Ubuntu, CentOS, Debian and SUSE), and Darwin. We recommend you to use g++ version
+on at least 4.4 (or above) in order to pass all the source code compilation. 
 
 */