[Debian-med-packaging] Bug#895924: libzstd FTCBFS: uses the build architecture compiler

[Helmut Grohne]

Source: libzstd
Version: 1.3.3+dfsg-1
Severity: important
Tags: patch
User: helmutg at debian.org
Usertags: rebootstrap
Control: affects -1 + src:apt

Congratulations! libzstd became part of the essential build closure as
apt started depending on it. Before too long libzstd will be on every
Debian system around.

Of course that means you get a lot more bug reports and this likely is
one of the first ones. Being part of the essential build closure is a
privilege that comes with some obligations. You need to be cross
buildable. Thus I'm filing this bug at important severity.

The actual cross build failure is rather simple and simply fixed.
dh_auto_build passes cross compilers around, so that part just works.
The later $(MAKE) invocation doesn't do that and compiles for the build
architecture instead. Replacing it with dh_auto_build makes cross
building work. I'm attaching a patch for your convenience.

Helmut