they run configure/autogen.sh.

If the environment variables CFLAGS and/or LDFLAGS are set, their values
are saved and appended to the values that are set in configure.in.

Example (csh-style, cope):

% setenv CFLAGS -D_REENTRANT
% ./autogen.sh


git-svn-id: http://svn.xiph.org/trunk/ao@1372 0101bb08-14d6-0310-b084-bc0e0c8e3800