Bug#984769: FTBFS: python-escript fails if DFLAGS is set

[Sven Mueller]

I should add:

dpkg-buildflags manpage does not list DFLAGS as a supported flag, but
explicitly mentioned that more flags might get added in the future if
needed for more languages.

DFLAGS was added with

commit d01d1f49c9734a39fc278f4d5b75444c96491023
Author: Guillem Jover 
Date:   Fri Nov 27 01:52:28 2020 +0100

dpkg-buildflags: Add support for DFLAGS

Add default value in Debian and derivatives for the flag.

It will get either -fdebug or -frelease depending on noopt presence in
DEB_BUILD_OPTIONS, but for now nothing else, as it seems common for D
project to use CPPFLAGS and CFLAGS anyway.

Closes: #975896

Bug#984769: FTBFS: python-escript fails if DFLAGS is set

[Sven Mueller]

Package: python-escript
Version: 5.6-2

In my build enviroments, the DFLAGS dpkg-buildflags option is set (to
'-frelease').
python-escript in site_cons/extractdebbuild.py does not know about this
flag but should actually ignore it, AFAICT.

Suggested fix: Add DFLAGS to the ignoreflags list in line 34 of
site_confs/extractbuilddeb.py

Cheers,
Sven