tests: make tests more resilient to optimizations by passing values to _blackHole

Without `_blackHole`, the optimizer may remove or make assumptions about values, which are not intended by the test.
This fixes the tests when running them in optimize mode and when OSSA modules are enabled.

This is part of rdar://140229560.

Author: eeckstein

validation-test/stdlib/Arrays.swift.gyb

@@ -16,6 +16,7 @@ let CopyToNativeArrayBufferTests = TestSuite("CopyToNativeArrayBufferTests")
 
 extension Array {
   func _rawIdentifier() -> Int {
+    _blackHole(self)
     return unsafeBitCast(self, to: Int.self)
   }
 }

validation-test/stdlib/Set.swift

@@ -16,6 +16,7 @@ import Foundation
 
 extension Set {
   func _rawIdentifier() -> Int {
+    _blackHole(self)
     return unsafeBitCast(self, to: Int.self)
   }
 }

validation-test/stdlib/SetAnyHashableExtensions.swift

@@ -145,7 +145,8 @@ SetTests.test("insert<Hashable>(_:)/CastTrap")
   }
 
   expectCrashLater()
-  _ = s.insert(TestHashableDerivedB(1010, identity: 3))
+  let (_, old) = s.insert(TestHashableDerivedB(1010, identity: 3))
+  _blackHole(old)
 }
 
 SetTests.test("update<Hashable>(with:)") {