Makefile.am: Add clang static analysis support

Makefile.am: Add clang static analysis support

Clang Static Analyzer is a source code analysis tool to find bugs. This
patch adds make target to trigger static analysis using below commands.

./boot.sh
For Clang: ./configure CC=clang --with-dpdk
For GCC: ./configure CC=gcc --with-dpdk CFLAGS="-std=gnu99"
make clang-analyze

Run 'scan-view <results dir>' command to examine the bug report.

Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy@intel.com>
Acked-By: Lance Richardson <lrichard@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>