[Syslog-ng-maintainers] Bug#949847: syslog-ng FTBFS: configure: error: syslog-ng requires bison 3.4 or later

[Helmut Grohne]

Source: syslog-ng
Version: 3.25.1-1
Severity: serious
Tags: ftbfs

syslog-ng fails to build from source in unstable. A build log contains:

| configure: error: syslog-ng requires bison 3.4 or later (traditional yacc is not enough). Your source tree seems to be from git, which doesn't have lib/cfg-grammar.c. Please install bison or use a distribution tarball.

This seems a bit strange since it earlier finds:

| checking for bison... bison -y

Reproducible by reproducible builds:
https://tests.reproducible-builds.org/debian/rbuild/unstable/amd64/syslog-ng_3.25.1-1.rbuild.log.gz

Helmut