[Test Only] Restrict '@const' test to optimized-stdlib builds

Author: artemcm

test/ConstValues/IntegerExpressions.swift

@@ -1,5 +1,6 @@
 // Constant globals on integer expressions
 // REQUIRES: swift_feature_CompileTimeValues
+// REQUIRES: optimized_stdlib
 // RUN: %target-swift-frontend -emit-ir -primary-file %s -parse-as-library -enable-experimental-feature CompileTimeValues -verify
 
 @const let constGlobal1: Int = (42 + 42 + 42) / 3