Bug#901348: unalz FTCBFS: uses the build architecture C++ compiler

[Helmut Grohne <helmut@subdivi.de>]

On Fri, Jun 15, 2018 at 06:13:40AM +0900, Changwoo Ryu wrote:
> How about using the makefile variable $(CXX) instead of environment
> variable, just for consistency.

make defaults CXX to plain g++, so unless you change the default, that's
broken for cross builds again. If you add

    -include /usr/share/dpkg/buildtools.mk

to your debian/rules, $(CXX) will be usable and your variant will work.

I chose this slightly strange variant, because it picks up the makefile
variable assigned by dh_auto_build and is thus quite short. Provided
that you set up CXX, your variant works as well.

Helmut