Part of the build system has support for optionally compiling mork (but the build fails if it isn't enabled) and other parts explicitly force that option to be on. Instead, just get rid of the option and always compile mork.
MozReview-Commit-ID: 8EV2uQyYZ01
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extra : rebase_source : 894b94b461fa8a138e9b781e81157793a3e9c705
extra : amend_source : 989e6ecddaabc0c7eca3cb30b43630c4994d2a2a
extra : histedit_source : 53f79f2cb127305b4d8a01abcec1a428ec41c340