Add basebrowser-incrementals-nightly makefile target
In order to create incrementals for basebrowser nightly builds (tor-browser-bundle-testsuite#40073 (closed)), we need to add a basebrowser-incrementals-nightly makefile target.
In order to create incrementals for basebrowser nightly builds (tor-browser-bundle-testsuite#40073 (closed)), we need to add a basebrowser-incrementals-nightly makefile target.