The LZ4 patches caused new compiler warnings. It's the same issue that was fixed at 71cbbbbe8 for gzip. I think they would've been visible in the CI environment, too.
https://buildfarm.postgresql.org/cgi-bin/show_stage_log.pl?nm=wrasse&dt=2022-02-12%2005%3A08%3A48&stg=make "/export/home/nm/farm/studio64v12_6/HEAD/pgsql.build/../pgsql/src/backend/replication/basebackup_lz4.c", line 87: warning: Function has no return statement : bbsink_lz4_new https://buildfarm.postgresql.org/cgi-bin/show_stage_log.pl?nm=bowerbird&dt=2022-02-12%2013%3A11%3A20&stg=make https://buildfarm.postgresql.org/cgi-bin/show_stage_log.pl?nm=hamerkop&dt=2022-02-12%2010%3A04%3A08&stg=make warning C4715: 'bbsink_lz4_new': not all control paths return a value https://buildfarm.postgresql.org/cgi-bin/show_stage_log.pl?nm=anole&dt=2022-02-12%2005%3A46%3A44&stg=make "basebackup_lz4.c", line 87: warning #2940-D: missing return statement at end of non-void function "bbsink_lz4_new" https://buildfarm.postgresql.org/cgi-bin/show_stage_log.pl?nm=wrasse&dt=2022-02-12%2005%3A08%3A48&stg=make "/export/home/nm/farm/studio64v12_6/HEAD/pgsql.build/../pgsql/src/backend/replication/basebackup_lz4.c", line 87: warning: Function has no return statement : bbsink_lz4_new
