LU-1199 build: Untangle the ldiskfs build system from lustre

LU-1199 build: Untangle the ldiskfs build system from lustre

Make ldiskfs have its own independant build system, with no
sharing of files from higher up the tree in lustre.  To begin
with, this means some minor duplication of functions in build
scripts.  However, it is my opinion that the simpicity that
is gained by having a clear separation of the build systems
far outweighs the costs of some initial duplication.  It
also opens up the possibility of easily moving ldiskfs into
its own separate git repo should we choose to do so in the
future.

The separation of the build systems began by removing the
ldiskfs/build->lustre/build symbolic link, and making a
complete copy of the lustre/build tree into ldiskfs/build.
Then I iterated on removing everything from ldiskfs/build
that was unnecessary to build ldiskfs.

Since lustre's build/autogen.sh is no longer shared between
two build systems, I removed the wrapper autogen.sh scripts
and made the upper-level autogen.sh in both lustre and
ldiskfs full-fledged scripts.  This meant making a minor
change to remove bash specific language (pushd/popd).

Now the ldiskfs subtree is capable of being built completely
absent of the lustre tree.  There are no doubt more things
that can be trimmed and cleaned up, but that much is now
complete.

Also, along the way I noted build/Makefile is being ignored
by git, even though it is part of the source tree, and not
auto-generated by the build system.  I added "!Makefile" to
.gitignore in the lustre/build directory so that it is no
longer ignored.

Change-Id: I98e437a0da897680e3ea6f21f15bcd6287367166
Signed-off-by: Christopher J. Morrone <morrone2@llnl.gov>
Reviewed-on: http://review.whamcloud.com/4409
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Brian J. Murrell <brian.murrell@intel.com>