Bug#994723: libimath-dev conflicts with libilmbase-dev

[Andrius Merkys <merkys@debian.org>]

Hi Matteo!

I attempted building opencolorio in unstable using libimath-dev built
from salsa [1]. opencolorio's dependencies pulled in libilmbase-dev
which resulted in both trying to write to
/usr/lib/x86_64-linux-gnu/libImath.so. I have no idea about these
conflicting packages, but the conflict has to be resolved prior to
moving on with opencolorio.

[1] https://salsa.debian.org/debian-phototools-team/imath.git, git
commit 34613b6d98747a002890453bce8117985f9f81bb

Best,
Andrius