src:forge fails to build on sparc64

[Ghislain Vaillant <ghisvail@gmail.com>]

Dear sparc64 porters,

I would like to draw your attention to a package I personally maintain
(src:forge) which FTBFS on sparc64 [1] only for an obscure reason. The
build log is available here [2] and the error line is pasted below:

make[3]: *** No rule to make target '/usr/lib/sparc64-linux-gnu/libGLU.so', needed by 'src/backend/opengl/libforge.so.0.9.2'.  Stop.

[1] https://buildd.debian.org/status/package.php?p=forge
[2] https://buildd.debian.org/status/fetch.php?pkg=forge&arch=sparc64&ver=0.9.2-1&stamp=1482401437

I'll be happy to apply any patch which could help the sparc64 build succeed.

Cheers,
Ghis