[LLDB][LoongArch] ObjectFile: add a case for `EM_LOONGARCH`

This adds the jump slot mapping for LoongArch. This is a simple
change that ensures lldb running properly.

 Note that this problem was found only when CMake variables
 "DLLVM_ENABLE_ASSERTIONS=ON" is selected.

Without this patch,

```
$ build/bin/lldb  test

../ELFHeader::GetRelocationJumpSlotType() const: Assertion `false && "architecture not supported"' fail

```
With this patch

```
$ build/bin/lldb  test
(lldb) target create "test"
Current executable set to '../test' (loongarch64).

```

Reviewed By: SixWeining, DavidSpickett

Differential Revision: https://reviews.llvm.org/D141245