Move build option explanations in how to build guide to scons help message

Resolves: COMPMID-5381

Change-Id: I556e2269ff6350f58509624a3d3d94cb0853cb8d
Signed-off-by: Michalis Spyrou <michalis.spyrou@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/7882
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Pablo Marquez Tello <pablo.tello@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>
diff --git a/tests/framework/SConscript b/tests/framework/SConscript
index 72208ea..450ffd7 100644
--- a/tests/framework/SConscript
+++ b/tests/framework/SConscript
@@ -30,8 +30,8 @@
 
 # vars is imported from arm_compute:
 variables = [
-    BoolVariable("pmu", "Enable PMU counters", False),
-    BoolVariable("mali", "Enable Arm® Mali™ hardware counters", False),
+    BoolVariable("pmu", "Enable the PMU cycle counter to measure execution time in benchmark tests. (Your device needs to support it)", False),
+    BoolVariable("mali", "Enable the collection of Arm® Mali™ hardware counters to measure execution time in benchmark tests. (Your device needs to have a Arm® Mali™ driver that supports it)", False),
 ]
 
 # We need a separate set of Variables for the Help message (Otherwise the global variables will get displayed twice)