Add feature to configure building with TIFF support.

[frewsxcv]

Thoughts? Would be a breaking change since it defaults to not building with TIFF support, and it used to

[urschrei]

I'm fine with it, but I think the network / grid download functionality requires libtiff – if we can't build with tiff support on M1, that's the fundamental problem.

[urschrei]

(Also, I'm in a writing hole until mid-next week, so I probably won't be able to do much other than talk about potential fixes)

[urschrei]

I think it's still an improvement to make tiff support optional (and probably contingent on the network feature). That potentially helps anyone not using the network feature and gives some way of building on M1.

You're absolutely correct.

[frewsxcv]

bors r=michaelkirk

[bors[bot]]

Build succeeded:

• ci result

[urschrei]

\o/