perf test: Add 'datasym' test workload

The datasym workload is to check if perf mem command gets the data
addresses precisely. This is needed for data symbol test.

$ perf test -w datasym

I had to keep the buf1 in the data section, otherwise it could end
up in the BSS and was mmaped as a separate //anon region, then it
was not symbolized at all. It needs to be fixed separately.

Committer notes:

Add a -U _FORTIFY_SOURCE to the datasym CFLAGS, as the main perf flags
set it and it requires building with optimization, and this new test has
a -O0.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zhengjun Xing <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20221116233854.1596378-12-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>