HPCC-15588 Changes to tbbmalloc_found conditional in commonSetup

Signed-off-by: Michael Gardner <Michael.Gardner@lexisnexis.com>

cmake_modules/commonSetup.cmake

@@ -859,12 +859,8 @@ IF ("${COMMONSETUP_DONE}" STREQUAL "")
         if (TBBMALLOC_FOUND)
           add_definitions (-D_USE_TBBMALLOC)
         else()
-          if(USE_OPTIONAL)
             message(WARNING "Optional TBBMALLOC requested, but missing")
             set(USE_TBBMALLOC OFF)
-          else()
-            message(FATAL_ERROR "TBB malloc proxy requested but package not found")
-          endif()
         endif()
       endif(USE_TBBMALLOC)