Add initial CentOS 3.9 root filesystem structure and essential scripts

- Created default user environment files: .bash_logout, .bash_profile, and .bashrc.
- Added symbolic links for dynamic linker and various libraries.
- Included essential binaries in /sbin for system management (e.g., fdisk, mkfs, hwclock).
- Implemented RPM verification script to check availability of required packages in CentOS vault.
- Established basic directory structure for logs and mail.
- Added a tarball for external libraries.

.gitignore

@@ -1,5 +1,6 @@
 output/
 usr/
-*.tar.gz
+*.iso
 rootfs/
 rpms/
+centos39-rootfs/