[Debian-med-packaging] Bug#791525: libtecla: FTBFS with DEB_CPPFLAGS_APPEND: make: invalid option -- 'D'

[Chris West (Faux)]

Source: libtecla
Version: 1.6.2-2
Severity: important
Tags: sid stretch
User: reproducible-builds at lists.alioth.debian.org
Usertags: ftbfs

Dear Maintainer,

The package fails to build when I use DEB_CPPFLAGS_APPEND:

$ DEB_CPPFLAGS_APPEND='-D__BROKEN__=1' dpkg-buildpackage
[..]
make[1]: Entering directory '/tmp/buildd/libtecla-1.6.2'
make: invalid option -- 'D'
make: invalid option -- '_'
make: invalid option -- 'F'

It looks like CPPFLAGS ends up unquoted, so make is called like:
$ make CPPFLAGS=-D__BROKEN__=1 -D_FORTIFY_SOURCE=2

....which it's quite unhappy about.

This breaks the reproducible builds builder:
https://reproducible.debian.net/rb-pkg/unstable/amd64/libtecla.html

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 3.19.0-21-generic (SMP w/8 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)