[BinaryFormat] Add LoongArch

[SixWeining]

Very straightforward but could you add some tests?

[xen0n]

In D138018#3927431, @SixWeining wrote:

Very straightforward but could you add some tests?

Hmm, it seems the two methods are not currently covered by unit tests. Do I have to add something new?

[MaskRay]

This was added for llvm-ifs which did not have thorough tests [Facepalm].

llvm/lib/BinaryFormat/ELF.cpp

return StringSwitch<uint16_t>(LowerArch)
       .Case("norc", EM_NORC)
       .Case("csr_kalimba", EM_CSR_KALIMBA)
       .Case("amdgpu", EM_AMDGPU)
       .Case("riscv", EM_RISCV)
       .Case("lanai", EM_LANAI)
       .Case("bpf", EM_BPF)
       .Case("ve", EM_VE)
       .Case("csky", EM_CSKY)
+      .Case("loongarch", EM_LOONGARCH)
       .Default(EM_NONE);
 }
 
 /// Convert an ELF's e_machine value into an architecture name.
 StringRef ELF::convertEMachineToArchName(uint16_t EMachine) {
   switch (EMachine) {
   case EM_NONE:
     return "None";
StringRef ELF::convertEMachineToArchName(uint16_t EMachine) {
   case EM_LANAI:
     return "lanai";
   case EM_BPF:
     return "bpf";
   case EM_VE:
     return "ve";
   case EM_CSKY:
     return "csky";
+  case EM_LOONGARCH:
+    return "loongarch";
   default:
     return "None";
   }
 }