Provide a way to redirect output of fabric-tna build to dev null

Change-Id: Ib4b8787daef193e6c4af09fb0fa00338a0970438
diff --git a/app-build.sh b/app-build.sh
index 4fd9d48..f955fbb 100755
--- a/app-build.sh
+++ b/app-build.sh
@@ -177,7 +177,7 @@
 
 function fabric-tna-build {
 	# This workaround is temporary - typically we need to build only the pipeconf
-	cd "${FABRIC_TNA_ROOT}" || exit 1 && make "${FABRIC_TNA_TARGETS[@]}"
+	cd "${FABRIC_TNA_ROOT}" || exit 1 && make "${FABRIC_TNA_TARGETS[@]}" SHOW_SENSITIVE_OUTPUT="${SHOW_SENSITIVE_OUTPUT:-false}"
 	cd ../
 	build_app "${FABRIC_TNA_ROOT}"/target \
 	"${FABRIC_TNA_ROOT}"/ "fabric-tna" \