rpmbuild w2.xzdio and multithreading

is there any way to set the two options below in .rpmmacros to use multi-threading? the shell-script below works in case of tar but XZ_OPT env is ignored by rpmbuild and seeking two hours the internet don't give any answer in case of tar --threads=0 improves performance dramatically on a modern CPU most of the time with a lot of idle cores %_binary_payload w2.xzdio %_source_payload w2.xzdio ______________________________________________ #!/bin/bash export XZ_OPT="-2 --threads=0" /usr/bin/nice -n 19 /usr/bin/tar -p -cJf $1.tar.xz $1