[GHC] #16253: Offer a shorthand for `--skip=_build/stage$n/compiler/.dependencies.mk`

[GHC]

#16253: Offer a shorthand for `--skip=_build/stage$n/compiler/.dependencies.mk`
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        Reporter:  sgraf             |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Build System      |              Version:  8.6.3
  (Hadrian)                          |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 > When working on a stage1 compiler, the slightest change in any of the
 files leads to rebuilding the dependency matrix, which takes 20-30s time.
 That makes for a very disruptive edit-compile cycle.

 This is mysterious to me. I thought that part of the wonderfulness of
 Shake and early cut-off was that all this repeated work is not done.

 So why is that not working?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16253#comment:2>
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