Bug#923445: ghc: FTBFS (The 'ghc-flag' directive is already registered to domain std)

[Santiago Vila]

Package: src:ghc
Version: 8.4.4+dfsg1-1
Severity: serious
Tags: ftbfs

Dear maintainer:

I tried to build this package in buster but it failed:

--------------------------------------------------------------------------------
[...]
 debian/rules binary-indep
dh binary-indep
   dh_update_autotools_config -i
   debian/rules override_dh_autoreconf
make[1]: Entering directory '/<<BUILDDIR>>/ghc-8.4.4+dfsg1'
dh_autoreconf perl -- boot
Creating libraries/ghc-prim/ghc.mk
Creating libraries/text/ghc.mk

[... snipped ...]

/usr/bin/sphinx-build -b html -d docs/users_guide/.doctrees-html -D latex_paper_size=letter docs/users_guide docs/users_guide/build-html/users_guide
Running Sphinx v1.8.4

Extension error:
The 'ghc-flag' directive is already registered to domain std
make[3]: *** [docs/users_guide/ghc.mk:16: docs/users_guide/build-html/users_guide/index.html] Error 2
make[2]: *** [Makefile:127: all] Error 2
make[2]: Leaving directory '/<<BUILDDIR>>/ghc-8.4.4+dfsg1'
dh_auto_build: make -j1 returned exit code 2
make[1]: *** [debian/rules:132: override_dh_auto_build] Error 2
make[1]: Leaving directory '/<<BUILDDIR>>/ghc-8.4.4+dfsg1'
make: *** [debian/rules:58: binary-indep] Error 2
dpkg-buildpackage: error: debian/rules binary-indep subprocess returned exit status 2
--------------------------------------------------------------------------------

The build was made in my autobuilder with "dpkg-buildpackage -A"
and it also fails here:

https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/ghc.html

If this is really a bug in one of the build-depends, please use reassign and affects,
so that this is still visible in the BTS web page for this package.

Thanks.