Fix cmake to handle missing NUMA_FOUND variable

In the case libnuma is not found, NUMA_FOUND is (can be?) not defined
instead of being set to 0.

Author: lucjaulmes

CMakeLists.txt

@@ -269,10 +269,11 @@ if (ENABLE_MULTITHREADING)
   else()
     include(FindPkgConfig)
     pkg_search_module(NUMA numa IMPORTED_TARGET GLOBAL)
-    compile_option(NUMA_AWARE ${NUMA_FOUND})
     if (${NUMA_FOUND})
+      compile_option(NUMA_AWARE ${NUMA_FOUND})
       target_link_libraries(QuEST PRIVATE PkgConfig::NUMA)
     else()
+      compile_option(NUMA_AWARE 0)
       message(WARNING "libnuma not found, QuEST will not be aware of numa locality")
     endif()
   endif()