Set TZ=UTC before calls to zip

[DavidPrevot]

This change allows to make the package build reproducible.

While working on the "reproducible builds" effort 1, we have noticed
that pdf.js could not be built reproducibly.

The attached patch removes timezone-varying timestamps from the
files compressed with zip. Once applied, pdf.js can be built
reproducibly in our current experimental framework.

Bug-Debian: https://bugs.debian.org/793127

[timvandermeij]

/botio-linux preview

[pdfjsbot]

From: Bot.io (Linux)

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Received

Command cmd_preview from @timvandermeij received. Current queue size: 0

Live output at: http://107.21.233.14:8877/1c545901c65d2ed/output.txt

[pdfjsbot]

From: Bot.io (Linux)

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Success

Full output at http://107.21.233.14:8877/1c545901c65d2ed/output.txt

Total script time: 0.67 mins

Published

• Viewer: http://107.21.233.14:8877/1c545901c65d2ed/web/viewer.html
• B2G Viewer: http://107.21.233.14:8877/1c545901c65d2ed/extensions/b2g/content/web/viewer.html
• Extension: http://107.21.233.14:8877/1c545901c65d2ed/extensions/firefox/pdf.js.xpi

[timvandermeij]

Good, thanks!

[Snuffleupagus]

There are other callers of zip in make.js, see https://github.com/mozilla/pdf.js/blob/master/make.js#L377, so shouldn't this have been set globally instead of just in one place!?

[timvandermeij]

I think this change is only useful for the XPI builds. node make publish is, as far as I can tell, and correct me if I'm wrong, only used by us to only once create the release package. We could make this change global for the sake of consistency (feel free to create a follow-up patch for that), although for the Debian people (and for how I understand the make commands) this patch should also be enough.