configure: introduce --enable-samples option

configure: introduce --enable-samples option

Running ./bootstrap.sh step, throws bunch of warnings related to
samples/c:

samples/c/Makefile.am:23: warning: variable 'empty_cgroup_v2_SOURCES' is defined but no program or
samples/c/Makefile.am:23: library has 'empty_cgroup_v2' as canonical name (possible typo)
samples/c/Makefile.am:17: warning: variable 'get_all_controller_SOURCES' is defined but no program or
samples/c/Makefile.am:17: library has 'get_all_controller' as canonical name (possible typo)
samples/c/Makefile.am:14: warning: variable 'get_controller_SOURCES' is defined but no program or
samples/c/Makefile.am:14: library has 'get_controller' as canonical name (possible typo)
samples/c/Makefile.am:15: warning: variable 'get_mount_point_SOURCES' is defined but no program or
samples/c/Makefile.am:15: library has 'get_mount_point' as canonical name (possible typo)
samples/c/Makefile.am:20: warning: variable 'get_procs_SOURCES' is defined but no program or
samples/c/Makefile.am:20: library has 'get_procs' as canonical name (possible typo)
samples/c/Makefile.am:18: warning: variable 'get_variable_names_SOURCES' is defined but no program or
samples/c/Makefile.am:18: library has 'get_variable_names' as canonical name (possible typo)
samples/c/Makefile.am:22: warning: variable 'logger_SOURCES' is defined but no program or
samples/c/Makefile.am:22: library has 'logger' as canonical name (possible typo)
samples/c/Makefile.am:16: warning: variable 'proctest_SOURCES' is defined but no program or
samples/c/Makefile.am:16: library has 'proctest' as canonical name (possible typo)
samples/c/Makefile.am:12: warning: variable 'read_stats_SOURCES' is defined but no program or
samples/c/Makefile.am:12: library has 'read_stats' as canonical name (possible typo)
samples/c/Makefile.am:10: warning: variable 'setuid_SOURCES' is defined but no program or
samples/c/Makefile.am:10: library has 'setuid' as canonical name (possible typo)
samples/c/Makefile.am:19: warning: variable 'test_named_hierarchy_SOURCES' is defined but no program or
samples/c/Makefile.am:19: library has 'test_named_hierarchy' as canonical name (possible typo)
samples/c/Makefile.am:13: warning: variable 'walk_task_SOURCES' is defined but no program or
samples/c/Makefile.am:13: library has 'walk_task' as canonical name (possible typo)
samples/c/Makefile.am:11: warning: variable 'walk_test_SOURCES' is defined but no program or
samples/c/Makefile.am:11: library has 'walk_test' as canonical name (possible typo)
samples/c/Makefile.am:21: warning: variable 'wrapper_test_SOURCES' is defined but no program or
samples/c/Makefile.am:21: library has 'wrapper_test' as canonical name (possible typo)
src/Makefile.am: installing 'build-aux/depcomp'

fix this by introducing --enable-samples option at configure, which by
default is disabled. If the user wishes to run the sample code, they
can build them by passing the configure option.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>