Bug#881770: jbuilder: library builds fail on byte-code-only architectures

["Aaron M. Ucko" <ucko@debian.org>]

Package: jbuilder
Version: 1.0~beta14-1
Severity: important
Tags: upstream
Control: affects -1 src:ocaml-migrate-parsetree

Builds of ocaml-migrate-parsetree on byte-code-only architectures
(armel, mips*, and some non-release architectures) have been failing:

  jbuilder build @install
  No rule found for _build/default/ocamlbuild_plugin/migrate_parsetree_ocamlbuild.cmx

It appears that when jbuilder encounters a library stanza with no
explicit modes setting, it always tries to produce both native and
byte-code versions, even when only the latter is an option on the
current architecture.  Please adjust the default modes setting to
reflect the availability of ocamlopt, as already done for executables
(at least according to
https://github.com/janestreet/jbuilder/blob/master/doc/jbuild.rst).

Thanks!

-- System Information:
Debian Release: buster/sid
  APT prefers testing
  APT policy: (500, 'testing'), (500, 'stable'), (300, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386, x32

Kernel: Linux 4.13.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages jbuilder depends on:
ii  libc6  2.24-17

jbuilder recommends no packages.

jbuilder suggests no packages.

-- no debconf information