Add support for OFI conduit in GASNet

GASNet's OFI conduit is used for the Slingshot network on Perlmutter
and Frontier. It takes an additional configuration, GASNet_SYSTEM,
configured for either slingshot10 or slingshot11.

cmake/legion.cmake

@@ -132,6 +132,7 @@ else()
 		  set(Legion_EMBED_GASNet_VERSION "GASNet-2022.3.0" CACHE STRING "GASNet version")
 		  set(Legion_NETWORKS "gasnetex" CACHE STRING "GASNet conduit")
 		  set(GASNet_CONDUIT ${FF_GASNET_CONDUIT})
+		  set(GASNet_SYSTEM ${FF_GASNET_SYSTEM})
 		elseif("${FF_LEGION_NETWORKS}" STREQUAL "ucx")
 		  set(ucx_ROOT ${UCX_PATH}/lib/cmake)
           message(STATUS "Find ucx: ${UCX_PATH}")

config/config.inc

@@ -118,6 +118,13 @@ if [ "$FF_LEGION_NETWORKS" = "gasnet" ]; then
     SET_LEGION_NETWORKS+=" -DFF_GASNET_CONDUIT=mpi"
   elif [ "$FF_GASNET_CONDUIT" = "udp" ]; then
     SET_LEGION_NETWORKS+=" -DFF_GASNET_CONDUIT=udp"
+  elif [ "$FF_GASNET_CONDUIT" = "ofi" ]; then
+    SET_LEGION_NETWORKS+=" -DFF_GASNET_CONDUIT=ofi"
+    if [ "$FF_GASNET_SYSTEM" = "slingshot11" ]; then
+      SET_LEGION_NETWORKS+=" -DFF_GASNET_SYSTEM=slingshot11"
+    elif [ "$FF_GASNET_SYSTEM" = "slingshot10" ]; then
+      SET_LEGION_NETWORKS+=" -DFF_GASNET_SYSTEM=slingshot10"
+    fi
   fi
 elif [ "$FF_LEGION_NETWORKS" = "ucx" ]; then
   SET_LEGION_NETWORKS+=" -DFF_LEGION_NETWORKS=ucx"

config/config.linux

@@ -61,6 +61,9 @@ FF_LEGION_NETWORKS=${FF_LEGION_NETWORKS:-}
 # select GASNET conduit
 FF_GASNET_CONDUIT=${FF_GASNET_CONDUIT:-ibv}
 
+# select GASNET system (usually with OFI conduit)
+FF_GASNET_SYSTEM=${FF_GASNET_SYSTEM:-slingshot11}
+
 # set UCX dir if Legion networks is set to ucx
 UCX_DIR=${UCX_DIR:-""}