Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0
Just in case it's not clear already, the message "sed: -: No such file
or directory" comes from a portability bug in master's nt/Makefile.in.
Its line 'sed -f- ${srcdir}/../lib/gnulib.mk > $@-t && \' is not
portable, as POSIX says that -f's operand must be a file name, not '-'.
Presumably macOS 'sed' does not support the GNU extension where 'sed
-f-' reads stdin.