[lldb] Fix TestWithLimitDebugInfo.py

The test was broken (in the sense that it was not testing what it was
supposed to test) in two ways:
- a Makefile refactor caused it to stop being built with
  -flimit-debug-info
- clang's constructor homing changed the "home" of the type

This patch fixes the Makefile, and modifies the source code to produce
the same result with both type homing strategies. Due to constructor
homing I had to use a different implicitly-defined function for the test
-- I chose the assignment operator.

I also added some sanity checks to the test to ensure that the test is
indeed operating on limited debug info.