Add an example for using a build profile

SConstruct

@@ -10,6 +10,14 @@ projectdir = "demo"
 
 localEnv = Environment(tools=["default"], PLATFORM="")
 
+# Build profiles can be used to decrease compile times.
+# You can either specify "disabled_classes", OR
+# explicitly specify "enabled_classes" which disables all other classes.
+# Modify the example file as needed and uncomment the line below or
+# manually specify the build_profile parameter when running SCons.
+
+# localEnv["build_profile"] = "build_profile.json"
+
 customs = ["custom.py"]
 customs = [os.path.abspath(path) for path in customs]