openjdk8 @8u362 fails to build when libjpeg-turbo is active

[fhgwright (Fred Wright)]

The openjdk8 build procedure looks for libjpeg, and if it's found, it opportunistically attempts to include JPEG support. But the build doesn't actually work in this case, failing with many link-time undefineds. The workaround is to temporarily deactivate libjpeg-turbo while building openjdk8.

A minimal fix would be to declare a conflicts_build against libjpeg-turbo, essentially documenting the above annoyance to the user.

A better fix would be to disable the opportunistic JPEG support, though it doesn't seem to have a configure option to do so.

An even better fix would be to make JPEG support actually work, possibly as a variant (which would mean also making the no-JPEG case work). This would require determining where the missing functions are supposed to come from.