per LFS instructions:
you should issue build commands for glibc outside of the source directory.
cd $LFS/packages (or whatever you put your .tar.gz files in)
tar -zxvf glibc-2.3.5.tar.gz
,,/configure etc etc
If you're using the LFS version of glibc that they tarballed up -- don't. 2.3.5 is now available on the public ftp archive, whereas it was not when the LFS book was being written.
Also, if you plan to use bash 3.0 and glibc 2.3.5, you're going to need a patch that they don't mention in the book: