Further reduce the number of parallel jobs when testiong LLDB under ASAN

Author: adrian-prantl

utils/build-script-impl

@@ -2368,7 +2368,7 @@ for host in "${ALL_HOSTS[@]}"; do
 
                 if [[ "${ENABLE_ASAN}" ]] ; then
                     # Limit the number of parallel tests
-                    LLVM_LIT_ARGS="${LLVM_LIT_ARGS} -j $(sysctl hw.physicalcpu | awk -v N=${BUILD_JOBS} '{ print (N < $2) ? N : $2 }')"
+                    LLVM_LIT_ARGS="${LLVM_LIT_ARGS} -j $(sysctl hw.physicalcpu | awk -v N=${BUILD_JOBS} '{ print (N < $2) ? N : int($2/2) }')"
                 fi
 
                 FILTER_SWIFT_OPTION="--filter=[sS]wift"