SAOC LLDB D integration: 13th Weekly Update

[Luís Ferreira]

Hi D community!

I'm here again, to describe what I've done during the thirteenth 
week of
Symmetry Autumn of Code. This week as a bit atypical as I got 
infected with
COVID-19 and this made me feel exhausted both physically and 
mentally.

## Working approach to fetch basic types

After digging a bit about the problem I found out there is no 
problem
specifically in Release builds, and a simple function called 
`Verify` is there
to double check if the type is correct for Debug builds. After 
fixing that
function, the LLDB can now dump some simple output about global 
TLS and non-TLS
variables:

```
(lldb) ta v
Global variables for app.d in app:
app.bar = <No TLS data currently exists for this thread.>

app.ptr = <could not resolve type>
app.foobar =
```

For now it only recognizes boolean types, but it can't show up 
the value since
LLDB doesn't know a way to dump it correctly.

You can try this version yourself using
[this](https://github.com/devtty63/llvm-project/tree/lldb-d/implement-typesystem-d)
branch.

## Decoupling and trivial patches

I pushed a patch to decouple DWARF to LLDB encoding logic from 
Clang DWARF AST
Parser, along with a trivial fix about duplicate map assignment:

- https://reviews.llvm.org/D115662
- https://reviews.llvm.org/D115663

## What is next?

I already started working on some helpers to fetch the LLDB 
Format, Encoding
and BasicType, along with other information about a type to 
properly display
them. I'm not sure how Milestone 4 is going to work, as I 
underestimated
the support for custom expessions.