keep unity build off

Author: lriggs

ci/scripts/jni_macos_build.sh

@@ -52,7 +52,7 @@ github_actions_group_end
 
 : "${ARROW_USE_CCACHE:=ON}"
 : "${CMAKE_BUILD_TYPE:=release}"
-: "${CMAKE_UNITY_BUILD:=ON}"
+: "${CMAKE_UNITY_BUILD:=OFF}"
 if [ "${ARROW_USE_CCACHE}" == "ON" ]; then
   github_actions_group_begin "ccache statistics before build"
   ccache -sv 2>/dev/null || ccache -s