Debbie build fails for PostgreSQL 11 with: postgres.h: No such file or directory

[strk]

See ​https://debbie.postgis.net/job/PostGIS_Regress/8453/console

gcc "-I../../liblwgeom" -g -O2 -fPIC -I/var/lib/jenkins/workspace/geos/rel-3.7.0devw64/include   -I/usr/include/libxml2 -I/usr/include -DHAVE_SFCGAL    -I/var/lib/jenkins/workspace/gdal/rel-2.2w64/include "-I../../libpgcommon"  -I../rt_core -I. -I./ -I/var/lib/jenkins/workspace/pg/rel/pg11w64/include/postgresql/server -I/var/lib/jenkins/workspace/pg/rel/pg11w64/include/postgresql/internal  -D_GNU_SOURCE   -c -o rtpg_geometry.o rtpg_geometry.c
rtpg_geometry.c:30:22: fatal error: postgres.h: No such file or directory
compilation terminated.
<builtin>: recipe for target 'rtpg_geometry.o' failed
make[2]: *** [rtpg_geometry.o] Error 1