perf test: Set PERF_EXEC_PATH for script execution

The task-analyzer.py script (actually every other scripts too) requires
PERF_EXEC_PATH env to find dependent libraries and scripts. For scripts
test to run correctly, it needs to set PERF_EXEC_PATH to the perf tool
source directory.

Instead of blindly update the env, let's check the directory structure
to make sure it points to the correct location.

Fixes: e8478b84d6ba ("perf test: add new task-analyzer tests")
Cc: Petar Gligoric <[e-mail]>
Cc: Hagen Paul Pfeifer <[e-mail]>
Cc: Aditya Gupta <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Acked-by: Ian Rogers <[e-mail]>
Signed-off-by: Namhyung Kim <[e-mail]>

tools/perf/tests/shell/test_task_analyzer.sh

···
 tmpdir=$(mktemp -d /tmp/perf-script-task-analyzer-XXXXX)
 err=0
 
+# set PERF_EXEC_PATH to find scripts in the source directory
+perfdir=$(dirname "$0")/../..
+if [ -e "$perfdir/scripts/python/Perf-Trace-Util" ]; then
+  export PERF_EXEC_PATH=$perfdir
+fi
+
 cleanup() {
   rm -f perf.data
   rm -f perf.data.old