Hadrian breaks when eventlog RTS ways are enabled

When fixing !1483 (closed) I found that hadrian breaks when the eventlog-enabled RTS ways are enabled:

$ hadrian/build.cabal.sh  --flavour=validate
Up to date
| Configure package 'unix'
...
| Configure package 'hp2ps'
# cabal-configure (for _build/stage1/utils/hp2ps/setup-config)
| Copy package 'rts'
# cabal-copy (for _build/stage1/lib/package.conf.d/rts-1.0.conf)
/home/ben/ghc/ghc/_build/stage1/rts/build/libHSrts-1.0_l-ghc8.9.0.20190919.so: copyFile: does not exist (No such file or directory)
Error when running Shake build system:
  at action, called at src/Rules.hs:70:19 in main:Rules
  at need, called at src/Rules.hs:92:5 in main:Rules
* Depends on: _build/stage1/lib/package.conf.d/rts-1.0.conf
* Raised the exception:
ExitFailure 1

Manually calling hadrian on _build/stage1/rts/build/libHSrts-1.0_l-ghc8.9.0.20190919.so causes the object to be built and allows the build to proceed a bit further (this time failing with a similar error for the l_thr way).

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