BUG_ON is a no-op if NDEBUG is defined, otherwise it is an assert.
Compiling with NDEBUG yields:

  bench/numa.c: In function ‘bind_to_cpu’:
  bench/numa.c:314:1: error: control reaches end of non-void function [-Werror=return-type]
    314 | }
        | ^
  bench/numa.c: In function ‘bind_to_node’:
  bench/numa.c:367:1: error: control reaches end of non-void function [-Werror=return-type]
    367 | }
        | ^

Add return statements to cover this case.
Reviewed-by: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20220428202912.1056444-1-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>