add test case checking return type

Author: WANGJIEKE

test/Interop/SwiftToCxx/core/unsigned-return-type-no-zext.cpp

@@ -0,0 +1,14 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-interop-build-clangxx -c %s -I %t -S -emit-llvm -o %t/ir.ll
+// RUN: %FileCheck %s < %t/ir.ll
+
+unsigned char getEnumTagi8(void *p);
+unsigned getEnumTagi32(void *p);
+
+void test(void *p) {
+  getEnumTagi8(p);
+  getEnumTagi32(p);
+}
+
+// CHECK: declare zeroext i8 @_Z12getEnumTagi8Pv(i8*) #1
+// CHECK: declare i32 @_Z13getEnumTagi32Pv(i8*) #1