Add speculative clang-interpreter test

Let's see how far this gets on the build servers. The application requires
native JIT and uses the C standard library, but hopefully we can get this
tested on at least some configurations.

Taking a lead from the clang-format tests, we'll just expect the executable to
get picked up from the build output path for now.

llvm-svn: 207950

clang/test/Misc/interpreter.c

@@ -0,0 +1,10 @@
+// RUN: clang-interpreter %s | FileCheck %s
+// REQUIRES: native, examples
+
+int printf(const char *, ...);
+
+int main() {
+  // CHECK: {{Hello world!}}
+  printf("Hello world!\n");
+  return 0;
+}