$ more config.log | grep readline
configure:18493: checking readline/readline.h usability
configure:18493: checking readline/readline.h presence
configure:18493: checking for readline/readline.h
configure:18495: checking for readline in -lreadline
configure:18520: gcc -o conftest -g conftest.c -lreadline >&5
configure:18631: checking for rl_completion_matches in -lreadline
configure:18656: gcc -o conftest -g conftest.c -lreadline -lreadline >&5
| #include <readline/readline.h>
ac_cv_header_readline_readline_h=yes
ac_cv_lib_readline_readline=yes
ac_cv_lib_readline_rl_completion_matches=yes