Interop: remove -O in test

Now that the integral constants are being materialized when importing
`constexpr` from C++, we can avoid the need for the optimizer to inline
the value.  Remove this workaround.

Author: compnerd

test/Interop/Cxx/static/constexpr-static-member-var.swift

@@ -1,7 +1,6 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-clang -std=c++11 -c %S/Inputs/static-member-var.cpp -I %S/Inputs -o %t/static-member-var.o
-// NOTE: we must use `-O` here to ensure that the constexpr value is inlined and no undefined reference remains.
-// RUN: %target-build-swift -O %s -I %S/Inputs -o %t/statics %t/static-member-var.o -Xfrontend -enable-cxx-interop
+// RUN: %target-build-swift %s -I %S/Inputs -o %t/statics %t/static-member-var.o -Xfrontend -enable-cxx-interop
 // RUN: %target-codesign %t/statics
 // RUN: %target-run %t/statics
 //