More pain.  I said

sh validate --fast --no-clean

and got this output

Error when running Shake build system:

  at action, called at src/Rules.hs:71:19 in main:Rules

  at need, called at src/Rules.hs:93:5 in main:Rules

* Depends on: _validatebuild/stage1/lib/package.conf.d/base-4.14.0.0.conf

  at need, called at src/Rules/Register.hs:113:5 in main:Rules.Register

* Depends on: _validatebuild/stage1/libraries/base/build/libHSbase-4.14.0.0-ghc8.11.0.20191201.so

  at need, called at src/Rules/Library.hs:146:5 in main:Rules.Library

* Depends on: _validatebuild/stage1/libraries/base/build/GHC/IO/Handle/Lock/Common.dyn_o

  at &%>, called at src/Rules/Compile.hs:54:7 in main:Rules.Compile

* Depends on: _validatebuild/stage1/libraries/base/build/GHC/IO/Handle/Lock/Common.dyn_o _validatebuild/stage1/libraries/base/build/GHC/IO/Handle/Lock/Common.dyn_hi

  at error, called at src/Development/Shake/Internal/Rules/Files.hs:245:13 in shake-0.18.3-593067565aafb558d09b4352b8abc327d8911a39a0e9abab2804b002b1ae536e:Development.Shake.Internal.Rules.Files

* Raised the exception:

Error, &%> rule failed to produce 1 file (out of 2)

  _validatebuild/stage1/libraries/base/build/GHC/IO/Handle/Lock/Common.dyn_o

  _validatebuild/stage1/libraries/base/build/GHC/IO/Handle/Lock/Common.dyn_hi – MISSING

I think I’m going to have to revert to ‘sh validate –legacy’.  Please let me know when I should try again with Hadrian.

Simon