MLECO-2853: update cmake flags for Armclang

* set CMP0123 policy to remove warning
* remove parentheses to avoid assert is always true warning

Change-Id: Ifcdf089183d750d7b00b345f5c4115c82d897def
diff --git a/build_default.py b/build_default.py
index 3971a05..c0cf8d1 100755
--- a/build_default.py
+++ b/build_default.py
@@ -72,8 +72,7 @@
 
     # 1. Make sure the toolchain is supported, and set the right one here
     supported_toolchain_ids = ["gnu", "arm"]
-    assert (toolchain in supported_toolchain_ids,
-        f"Toolchain must be from {supported_toolchain_ids}")
+    assert toolchain in supported_toolchain_ids, f"Toolchain must be from {supported_toolchain_ids}"
     if toolchain == "arm":
         toolchain_file_name = "bare-metal-armclang.cmake"
     elif toolchain == "gnu":