apacheGH-41061: [C++] Ignore ARROW_USE_MOLD/ARROW_USE_LLD with clang …

…< 12 (apache#41062)

### Rationale for this change

`--ld-path` is available since clang 12 or later.

### What changes are included in this PR?

Ignore `ARROW_USE_MOLD`/`ARROW_USE_LLD` with clang < 12.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

Yes.
* GitHub Issue: apache#41061

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>

cpp/cmake_modules/SetupCxxFlags.cmake

@@ -679,7 +679,12 @@ if(ARROW_USE_LLD)
         )
       endif()
     elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-      set(LLD_LINKER_FLAGS "--ld-path=${LD_LLD}")
+      if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "12.0.0")
+        set(LLD_LINKER_FLAGS "--ld-path=${LD_LLD}")
+      else()
+        message(STATUS "Need clang 12.0.0 or later to use LLD linker: ${CMAKE_CXX_COMPILER_VERSION}"
+        )
+      endif()
     else()
       message(STATUS "Using the default linker because compiler doesn't support LLD: ${CMAKE_CXX_COMPILER_ID}"
       )