Originally I thought this was caused by the changes that happened in the
previous commit, but apparently not, and it was due to an unrelated
system upgrade I did -- the 1.2.202 Arch package had libvulkan.so link
to libpthread.so, but the 1.2.203 build not (and I couldn't reproduce
when rebuilding the 1.2.203 package from scratch, so I guess there was
some weird hiccup on the machine that used to build the package?). And
to make things worse, this caused a problem only when passing
`--magnum-device cpu` to select SwiftShader, which (unlike other
drivers, apparently) relies on pthread being linked in.
Nevertheless, Magnum should be immune against such issues same as it's
trying to be immune against Assimp regressions, so let's just link to
pthread always in the Find module, and do it via -pthread instead of
-lpthread so the same issue with the reference DCEd doesn't happen to
us.
Vladimír Vondruš
f96b76e2bf