give a chance to sparc64

Index: cpp/cmake_modules/SetupCxxFlags.cmake
--- cpp/cmake_modules/SetupCxxFlags.cmake.orig
+++ cpp/cmake_modules/SetupCxxFlags.cmake
@@ -38,6 +38,8 @@ if(NOT DEFINED ARROW_CPU_FLAG)
     set(ARROW_CPU_FLAG "s390x")
   elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "riscv64")
     set(ARROW_CPU_FLAG "riscv64")
+  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "sparc64")
+    set(ARROW_CPU_FLAG "sparc64")
   elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "loongarch64")
     set(ARROW_CPU_FLAG "loongarch64")
   else()
