GH-47469: [C++][Gandiva] Add support for LLVM 21.1.0 (#47473)

### Rationale for this change

LLVM 21.1 was released and some of our CI jobs are failing.

### What changes are included in this PR?

* Accept LLVM 21.1
* Don't use deprecated API

Two of the related commits that changed APIs on LLVM are:
- llvm/llvm-project@034f2b3
- llvm/llvm-project@b18e5b6

### Are these changes tested?

Yes on CI

### Are there any user-facing changes?

No

* GitHub Issue: #47469

Authored-by: Raúl Cumplido <[email protected]>
Signed-off-by: Sutou Kouhei <[email protected]>

Author: raulcd

cpp/CMakeLists.txt

@@ -177,6 +177,7 @@ set(ARROW_DOC_DIR "share/doc/${PROJECT_NAME}")
 set(BUILD_SUPPORT_DIR "${CMAKE_SOURCE_DIR}/build-support")
 
 set(ARROW_LLVM_VERSIONS
+    "21.1"
     "20.1"
     "19.1"
     "18.1"

cpp/src/gandiva/engine.cc

@@ -202,10 +202,16 @@ Status UseJITLinkIfEnabled(llvm::orc::LLJITBuilder& jit_builder) {
   static auto maybe_use_jit_link = ::arrow::internal::GetEnvVar("GANDIVA_USE_JIT_LINK");
   if (maybe_use_jit_link.ok()) {
     ARROW_ASSIGN_OR_RAISE(static auto memory_manager, CreateMemmoryManager());
+#  if LLVM_VERSION_MAJOR >= 21
+    jit_builder.setObjectLinkingLayerCreator([&](llvm::orc::ExecutionSession& ES) {
+      return std::make_unique<llvm::orc::ObjectLinkingLayer>(ES, *memory_manager);
+    });
+#  else
     jit_builder.setObjectLinkingLayerCreator(
         [&](llvm::orc::ExecutionSession& ES, const llvm::Triple& TT) {
           return std::make_unique<llvm::orc::ObjectLinkingLayer>(ES, *memory_manager);
         });
+#  endif
   }
   return Status::OK();
 }

cpp/src/gandiva/llvm_types.h

@@ -56,7 +56,11 @@ class GANDIVA_EXPORT LLVMTypes {
   llvm::Type* double_type() { return llvm::Type::getDoubleTy(context_); }
 
   llvm::PointerType* ptr_type(llvm::Type* type) {
+#if LLVM_VERSION_MAJOR >= 21
+    return llvm::PointerType::get(context_, 0);
+#else
     return llvm::PointerType::get(type, 0);
+#endif
   }
 
   llvm::PointerType* i8_ptr_type() { return ptr_type(i8_type()); }