[GHC] #16051: Cross compilation broken under Hadrian

[GHC]

#16051: Cross compilation broken under Hadrian
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:  alpmestan
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.8.1
       Component:  Build System      |              Version:  8.7
  (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 alpmestan):

 ghctags being gone, I don't have any problem getting the build to complete
 with this very simple patch:

 {{{#!diff
 diff --git a/hadrian/src/UserSettings.hs b/hadrian/src/UserSettings.hs
 index c92dd11d44..b6fc30bd90 100644
 --- a/hadrian/src/UserSettings.hs
 +++ b/hadrian/src/UserSettings.hs
 @@ -59,4 +59,4 @@ successColour = mkSuccessColour (Dull Green)
  -- 'Stage1' compiler. Setting it to 'Stage3' will build the 'Stage3'
  -- compiler. Setting it to 'Stage0' will mean nothing gets built at all.
  finalStage :: Stage
 -finalStage = Stage2
 +finalStage = Stage1
 }}}

 (this is a setting Matthew introduced somewhat recently, documented in
 hadrian's docs)

 With this in place, a simple `hadrian/build.sh -j4` builds stage 1 to
 completion. However, trying to build this trivial Haskell program then
 fails:

 {{{#!hs
 main = putStrLn "hello"
 }}}

 with

 {{{#!sh
 $ _build/stage0/bin/aarch64-unknown-linux-gnu-ghc hello.hs -o hello
 [1 of 1] Compiling Main             ( hello.hs, hello.o )

 hello.hs:1:1: error:
     Bad interface file: /nix/store/8h3fdgpq66w8kxzxn49s706505a7ihnr-
 ghc-8.4.3/lib/ghc-8.4.3/base-4.11.1.0/Prelude.hi
         mismatched interface file versions (wanted "80720190211", got
 "8043")
   |
 1 | main = putStrLn "hello"
   | ^
 }}}

 The cross-compiler ends up looking at the boot compiler's interface files
 instead of its own.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16051#comment:6>
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