[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