44ff8df777
m4 was hugely popular in the past, because autotools, automake, flex, bison and many other things used it. But nowadays it much less popular, and might not even be installed in the buildroot. (m4 is small, so it doesn't make a big difference.) (FWIW, Fedora dropped make from the buildroot now, https://fedoraproject.org/wiki/Changes/Remove_make_from_BuildRoot. I think it's reasonable to assume that m4 will be dropped at some point too.) The main reason to drop m4 is that the syntax is not very nice, and we should minimize the number of different syntaxes that we use. We still have two (configure_file() with @FOO@ and jinja2 templates with {{foo}} and the pythonesque conditional expressions), but at least we don't need m4 (with m4_dnl and `quotes').
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