[Orc] Let LLJIT default to JITLink for ELF-based ARM targets (#77313)

The JITLink AArch32 backend reached feature-parity with RuntimeDyld
on ELF-based systems. This patch changes the default JIT-linker in Orc's
LLJIT for these platforms.

This allows us to run clang-repl with JITLink on ARM and use all the
features we had with RuntimeDyld before. All existing tests for
clang-repl are passing.

llvm/lib/ExecutionEngine/Orc/LLJIT.cpp

@@ -734,6 +734,12 @@ Error LLJITBuilderState::prepareForConstruction() {
     case Triple::aarch64:
       UseJITLink = !TT.isOSBinFormatCOFF();
       break;
+    case Triple::arm:
+    case Triple::armeb:
+    case Triple::thumb:
+    case Triple::thumbeb:
+      UseJITLink = TT.isOSBinFormatELF();
+      break;
     case Triple::x86_64:
       UseJITLink = !TT.isOSBinFormatCOFF();
       break;