all.sh: rename a helper function

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 0eedc88..58af8ef 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -445,7 +445,7 @@
     echo "******************************************************************"
 }
 
-armc6_build_test()
+helper_armc6_build_test()
 {
     FLAGS="$1"