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

[lh03061238]

Summary

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).

[DavidSpickett]

LGTM.

lldb/source/Plugins/ObjectFile/ELF/ELFHeader.cpp

case EM_MIPS:
     slot = R_MIPS_JUMP_SLOT;
     break;
   case EM_S390:
     slot = R_390_JMP_SLOT;
     break;
   case EM_RISCV:
     slot = R_RISCV_JUMP_SLOT;
     break;
+  case EM_LOONGARCH:
+    slot = R_LARCH_JUMP_SLOT;
+    break;
   }
 
   return slot;
 }
 
 // ELFSectionHeader
 
 ELFSectionHeader::ELFSectionHeader() {