Merge pull request #17416 from viktor-ferenczi/issue-17414

Avoid confusing traceback on attempting build without platform option

SConstruct

@@ -491,6 +491,7 @@ else:
     for x in platform_list:
         print("\t" + x)
     print("\nPlease run scons again with argument: platform=<string>")
+    sys.exit(255)
 
 
 screen = sys.stdout