Add a test for class members in a custom section

Since there were some problems with the result of these cases, leading to invalid assembly/object code on some platforms.
Fixed by https://reviews.llvm.org/D147184.

Differential Revision: https://reviews.llvm.org/D154673

Author: daltenty

SingleSource/Regression/C++/custom_section_members.cpp

@@ -0,0 +1,14 @@
+// Test that we can compile a simple class with members in a custom section.
+
+struct A {
+  static int foo() __attribute__((section("section")));
+  static void bar() __attribute__((section("section")));
+};
+
+int A::foo() { return 0; }
+void A::bar() {}
+
+int main() {
+  A::bar();
+  return A::foo();
+}

SingleSource/Regression/C++/custom_section_members.reference_output

@@ -0,0 +1 @@
+exit 0