Sharing the datastores across the clusters is still possible. If you have mounted the LUN on first ESXi and formatted the datastores with VMFS, you should be able to see it on the other ESXi also. If you are unable to see, try rescan the HBA/datastores on the ESXis.
If you were asked to reformat the LUN even after formatting with VMFS on first host, please re-check on how its presented from the storage end.
For more information, see https://communities.vmware.com/thread/337600