[ORC-RT] Test basic C++ static initialization support in the ORC runtime.

This tests that a simple C++ static initializer works as expected.

Compared to the architecture specific, assembly level regression tests for the
ORC runtime; this test is expected to catch cases where the compiler adopts
some new MachO feature that the ORC runtime does not yet support (e.g. a new
initializer section).

Author: lhames

compiler-rt/test/orc/TestCases/Darwin/Generic/trivial-cxx-constructor.cpp

@@ -0,0 +1,17 @@
+// RUN: %clangxx -c -o %t %s
+// RUN: %llvm_jitlink %t
+//
+// REQUIRES: system-darwin && host-arch-compatible
+
+static int x = 1;
+
+class Init {
+public:
+  Init() { x = 0; }
+};
+
+static Init I;
+
+int main(int argc, char *argv[]) {
+  return x;
+}