Add build timeout

[martincostello]

Timeout the build after 15 minutes.

Otherwise it will potentially run for up to 6 hours(!) if something goes wrong.

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.47%. Comparing base (0fab2d5) to head (e15b95c).

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3370   +/-   ##
=======================================
  Coverage   83.47%   83.47%           
=======================================
  Files          84       84           
  Lines        3280     3280           
  Branches      572      572           
=======================================
  Hits         2738     2738           
  Misses        542      542           

Flag	Coverage Δ
Linux	83.47% <ø> (ø)
Windows	83.47% <ø> (ø)
macOS	83.47% <ø> (ø)

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