Not surprisingly (given discussion earlier in this thread), reverting the part of r26309 pertaining to config/init/hints/darwin.pm resolved this problem, quieting config/auto/readline.pm during configuration.
Determining if your platform supports readline..........................no. See patch attached, undo.26309.hints.darwin.patch.txt
Index: config/init/hints/darwin.pm =================================================================== --- config/init/hints/darwin.pm (revision 26379) +++ config/init/hints/darwin.pm (working copy) @@ -24,6 +24,9 @@ my $lib_dir = $conf->data->get('build_dir') . "/blib/lib"; $ldflags .= " -L$lib_dir"; $ccflags .= " -pipe -fno-common -Wno-long-double "; + $ccflags =~ s/-flat_namespace\s*//; + $ldflags =~ s/-flat_namespace\s*//; + $ldflags .= " -flat_namespace "; $conf->data->set( darwin => 1, @@ -34,10 +37,9 @@ share_ext => '.dylib', load_ext => '.bundle', link => 'c++', - linkflags => '-undefined dynamic_lookup', ld => 'c++', - ld_share_flags => '-dynamiclib -undefined dynamic_lookup', - ld_load_flags => '-bundle -undefined dynamic_lookup', + ld_share_flags => '-dynamiclib -undefined suppress', + ld_load_flags => '-bundle -undefined suppress', memalign => 'some_memalign', has_dynamic_linking => 1,