armadillo @8.200.1 +arpack: 'mpi.h' file not found

[majoc-at-astro (majoc-at-astro)]

Log from last Friday's build run to be attached. Here's the top bit:

:info:build In file included from /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_science_armadillo/armadillo/work/armadillo-8.200.1/src/wrapper.cpp:51:
:info:build In file included from /opt/local/include/hdf5.h:22:
:info:build /opt/local/include/H5public.h:59:13: fatal error: 'mpi.h' file not found
:info:build #   include <mpi.h>
:info:build             ^~~~~~~
:info:build 1 error generated.

This is on macOS 10.12 with Xcode 9.0, with arpack @3.4.0_2+accelerate+gcc6 having already been successfully built; it occurs also on 10.11 with Xcode 8.3.3, and first started in early September. Annoyingly, it only seems to happen in production builds, and it consistently fails to fail when attempted on a build which is otherwise empty.

Please let me know if there's any more information you need, or what other tests to make. Please see also ​https://trac.macports.org/ticket/55080, which started failing the same way at the same time, but which does fail on an empty build.

[majoc-at-astro (majoc-at-astro)]

Build log for armadillo +arpack from production