I've downloaded, built and installed glibc many times before and all was ok, this time ldconfig binary is not created and hence I am unable to update the /etc/ld.so.cache file correctly leading to a problem finding shared objetcts. The version of glibc with this behaviour is glibc-2.20, I am using a custom linux distribution built initially with the help of the Linux From Scractch Book, custom linux also and x86_64 architecture.
I've tried changing the configure options and also tried to compile without any option at all.
I solved it, there is a variable in the configure script use_ldconfig it was set to no, setting it to yes did solve the problem.