perf test: Do not fail Intel-PT misc test w/o libpython

The virtual LBR test uses a python script to check the max size of
branch stack in the Intel-PT generated LBR. But it didn't check whether
python scripting is available (as it's optional).

Let's skip the test if the python support is not available.

Fixes: f77811a0f62577d2 ("perf test: test_intel_pt.sh: Add 9 tests")
Reviewed-by: Adrian Hunter <[e-mail]>
Signed-off-by: Namhyung Kim <[e-mail]>
Acked-by: Ian Rogers <[e-mail]>
Cc: Ammy Yi <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/shell/test_intel_pt.sh

···
 test_virtual_lbr()
 {
 	echo "--- Test virtual LBR ---"
+	# Check if python script is supported
+	libpython=$(perf version --build-options | grep python | grep -cv OFF)
+	if [ "${libpython}" != "1" ] ; then
+		echo "SKIP: python scripting is not supported"
+		return 2
+	fi
 
 	# Python script to determine the maximum size of branch stacks
 	cat << "_end_of_file_" > "${maxbrstack}"