LU-2752 build: Enhance build for cross compilation for MIC

Enhance lustre build for cross compilation for the Intel(R) Xeon
Phi(TM) card. In addition to standard build the GNU cross
toolchain for the Intel(R) Xeon Phi(TM) can be used to produce
client binaries for the Intel(R) Xeon Phi(TM) card. To enable
this just specify appropriate --host and --build option for
./configure.

For example, to produce Lustre client binaries for Intel(R) Xeon
Phi(TM) card just execute the following commands:

NOTE: You should have "intel-mic-gpl-<version>.x86_64" package
installed and MIC GPL sources unpacked in /opt/intel/mic/src.

export PATH=/usr/linux-k1om-4.7/bin:$PATH

sh ./autogen.sh

./configure --with-linux=/opt/intel/mic/src/card/kernel \
    --disable-server --without-o2ib \
    --host=x86_64-k1om-linux --build=x86_64-pc-linux

make

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: I4347c65f67bd836116532989c2132457f5eee934
Reviewed-on: http://review.whamcloud.com/5273
Tested-by: Hudson
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>