Help!(Installing GCC.)

(Installing GCC: Configuration)

In the document of Installing GCC, there is a sentence I don't
understand:
" Second, when configuring a native system, either cc or gcc must be in your path or you must set CC in your environment before running configure. Otherwise the configuration scripts may fail. "
How to do ?
Thanks!

CC=/usr/bin/cc
export CC

Of course, this assumes that you have a cc compiler at the path /usr/bin/cc. If not, change the first line to whatever works for you.

Or, for an even quicker fix, try this:
(as suggested in the documentation)
CC=/path/to/compiler/cc ./configure

It should set the CC variable, then run "configure", with your settings reflected. (Note the space inbetween "cc" and "./configure")