[cxx-interop] Re-enable a test for C foreign reference types

This test has been disabled since 2022.

This re-enables the test in order to have  some test coverage of the `-experimental-c-foreign-reference-types` compiler flag.

See `test/Interop/Cxx/foreign-reference/reference-counted.swift` for a very similar test that enables C++ interop.

rdar://101790203

Author: egorzhdan

test/Interop/C/struct/foreign-reference.swift

@@ -1,9 +1,9 @@
-// RUN: %target-run-simple-swift(-I %S/Inputs/ -Xfrontend -validate-tbd-against-ir=none -Xfrontend -experimental-c-foreign-reference-types)
+// RUN: %target-run-simple-swift(-I %S/Inputs/ -Xfrontend -validate-tbd-against-ir=none -Xfrontend -experimental-c-foreign-reference-types -Onone -D NO_OPTIMIZATIONS)
+// RUN: %target-run-simple-swift(-I %S/Inputs/ -Xfrontend -validate-tbd-against-ir=none -Xfrontend -experimental-c-foreign-reference-types -O)
 //
 // REQUIRES: executable_test
 // TODO: This should work without ObjC interop in the future rdar://97497120
 // REQUIRES: objc_interop
-// REQUIRES: rdar101790203
 
 import StdlibUnittest
 import ForeignReference
@@ -15,24 +15,32 @@ public func blackHole<T>(_ _: T) {  }
 
 ReferenceCountedTestSuite.test("Local") {
     var x = createLocalCount()
+#if NO_OPTIMIZATIONS
     expectEqual(x.value, 6) // This is 6 because of "var x" "x.value" * 2 and "(x, x, x)".
+#endif
 
     let t = (x, x, x)
+#if NO_OPTIMIZATIONS
     expectEqual(x.value, 5)
+#endif
 }
 
 @inline(never)
 func globalTest1() {
     var x = createGlobalCount()
     let t = (x, x, x)
+#if NO_OPTIMIZATIONS
     expectEqual(globalCount, 4)
+#endif
     blackHole(t)
 }
 
 @inline(never)
 func globalTest2() {
     var x = createGlobalCount()
+#if NO_OPTIMIZATIONS
     expectEqual(globalCount, 1)
+#endif
 }
 
 ReferenceCountedTestSuite.test("Global") {