Mentioned -opt in the README.

README.md

@@ -4,7 +4,7 @@ Download dependencies:
 
 	./gradlew dependencies:update
 
-Then build the compiler
+Then build the compiler:
 
 	./gradlew dist
 
@@ -12,6 +12,10 @@ After that you should be able to compile your programs like that:
 
 	./dist/bin/konanc hello.kt -o hello
 
+For an optimized compilation use -opt:
+
+	./dist/bin/konanc hello.kt -o hello -opt
+
 For more tests, use:
 
 	./gradlew backend.native:tests:run