I can see relevant logs in the latest LP buildlog:
```
 debian/rules build
autoconf
configure.in:11: warning: The macro `AC_CONFIG_HEADER' is obsolete.
configure.in:11: You should run autoupdate.
./lib/autoconf/status.m4:719: AC_CONFIG_HEADER is expanded from...
configure.in:11: the top level
configure.in:82: warning: The macro `AC_CANONICAL_SYSTEM' is obsolete.
configure.in:82: You should run autoupdate.
./lib/autoconf/general.m4:2081: AC_CANONICAL_SYSTEM is expanded from...
configure.in:82: the top level
configure.in:86: warning: AC_PROG_LEX without either yywrap or noyywrap is obsolete
./lib/autoconf/programs.m4:716: _AC_PROG_LEX is expanded from...
./lib/autoconf/programs.m4:709: AC_PROG_LEX is expanded from...
configure.in:86: the top level
configure.in:95: warning: The macro `AC_HEADER_STDC' is obsolete.
configure.in:95: You should run autoupdate.
./lib/autoconf/headers.m4:704: AC_HEADER_STDC is expanded from...
configure.in:95: the top level
configure.in:124: warning: The macro `AC_CHECKING' is obsolete.
configure.in:124: You should run autoupdate.
./lib/autoconf/general.m4:2499: AC_CHECKING is expanded from...
configure.in:124: the top level
configure.in:136: warning: The macro `AC_CHECKING' is obsolete.
configure.in:136: You should run autoupdate.
./lib/autoconf/general.m4:2499: AC_CHECKING is expanded from...
configure.in:136: the top level
configure.in:170: warning: The macro `AC_CHECKING' is obsolete.
configure.in:170: You should run autoupdate.
./lib/autoconf/general.m4:2499: AC_CHECKING is expanded from...
configure.in:170: the top level
configure.in:180: warning: The macro `AC_CHECKING' is obsolete.
configure.in:180: You should run autoupdate.
./lib/autoconf/general.m4:2499: AC_CHECKING is expanded from...
configure.in:180: the top level
configure.in:197: warning: The macro `AC_CHECKING' is obsolete.
configure.in:197: You should run autoupdate.
./lib/autoconf/general.m4:2499: AC_CHECKING is expanded from...
configure.in:197: the top level
configure.in:212: warning: The macro `AC_CHECKING' is obsolete.
configure.in:212: You should run autoupdate.
./lib/autoconf/general.m4:2499: AC_CHECKING is expanded from...
configure.in:212: the top level
configure.in:231: warning: The macro `AC_CHECKING' is obsolete.
configure.in:231: You should run autoupdate.
./lib/autoconf/general.m4:2499: AC_CHECKING is expanded from...
configure.in:231: the top level
configure.in:288: warning: AC_OUTPUT should be used without arguments.
configure.in:288: You should run autoupdate.
```

Which is resolved after applying the debdiff:
```
 debian/rules build
autoupdate
autoupdate: warning: autoconf input should be named 'configure.ac', not 'configure.in'
configure.in:95: warning: The preprocessor macro `STDC_HEADERS' is obsolete.
  Except in unusual embedded environments, you can safely include all
  ISO C90 headers unconditionally.
autoconf
configure.in:86: warning: AC_PROG_LEX without either yywrap or noyywrap is obsolete
./lib/autoconf/programs.m4:716: _AC_PROG_LEX is expanded from...
./lib/autoconf/programs.m4:709: AC_PROG_LEX is expanded from...
configure.in:86: the top level
configure.in:95: warning: The preprocessor macro `STDC_HEADERS' is obsolete.
configure.in:95:   Except in unusual embedded environments, you can safely include all
configure.in:95:   ISO C90 headers unconditionally.
[...]
checking for fork... yes
checking for vfork... yes
checking for working fork... yes
checking for working vfork... (cached) yes
```

LGTM. Sponsored into Noble