race condition in hadrian on master?

Summary

hadrian has some sort of race condition

Steps to reproduce

./hadrian/build.sh --flavour=perf  -j8
Up to date
| Run Ghc CompileHs Stage1: libraries/Cabal/Cabal/Distribution/Simple/Setup.hs => _build/stage1/libraries/Cabal/Cabal/build/Distribution/Simple/Setup.o
| Run Ghc CompileHs Stage1: libraries/Cabal/Cabal/Distribution/Simple/Setup.hs => _build/stage1/libraries/Cabal/Cabal/build/Distribution/Simple/Setup.p_o
| Run Ghc CompileHs Stage1: compiler/cmm/CmmProcPoint.hs => _build/stage1/compiler/build/CmmProcPoint.o
| Run Ghc CompileHs Stage1: compiler/llvmGen/Llvm/PpLlvm.hs => _build/stage1/compiler/build/Llvm/PpLlvm.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/SPARC/Stack.hs => _build/stage1/compiler/build/SPARC/Stack.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/PPC/Instr.hs => _build/stage1/compiler/build/PPC/Instr.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/NCGMonad.hs => _build/stage1/compiler/build/NCGMonad.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/RegAlloc/Graph/Stats.hs => _build/stage1/compiler/build/RegAlloc/Graph/Stats.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/SPARC/Instr.hs => _build/stage1/compiler/build/SPARC/Instr.o
| Run Ghc CompileHs Stage1: compiler/llvmGen/Llvm.hs => _build/stage1/compiler/build/Llvm.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/RegAlloc/Graph/Main.hs => _build/stage1/compiler/build/RegAlloc/Graph/Main.o
| Run Ghc CompileHs Stage1: compiler/GHC/StgToCmm/Expr.hs => _build/stage1/compiler/build/GHC/StgToCmm/Expr.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/BlockLayout.hs => _build/stage1/compiler/build/BlockLayout.o
| Run Ghc CompileHs Stage1: compiler/cmm/CmmLayoutStack.hs => _build/stage1/compiler/build/CmmLayoutStack.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/PPC/RegInfo.hs => _build/stage1/compiler/build/PPC/RegInfo.o
| Run Ghc CompileHs Stage1: compiler/llvmGen/LlvmCodeGen/Regs.hs => _build/stage1/compiler/build/LlvmCodeGen/Regs.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/PPC/Ppr.hs => _build/stage1/compiler/build/PPC/Ppr.o
| Run Ghc CompileHs Stage1: compiler/GHC/StgToCmm/Bind.hs => _build/stage1/compiler/build/GHC/StgToCmm/Bind.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/SPARC/CodeGen/Expand.hs => _build/stage1/compiler/build/SPARC/CodeGen/Expand.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/SPARC/Ppr.hs => _build/stage1/compiler/build/SPARC/Ppr.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/SPARC/ShortcutJump.hs => _build/stage1/compiler/build/SPARC/ShortcutJump.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/SPARC/CodeGen/Base.hs => _build/stage1/compiler/build/SPARC/CodeGen/Base.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/X86/Instr.hs => _build/stage1/compiler/build/X86/Instr.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/SPARC/CodeGen/Sanity.hs => _build/stage1/compiler/build/SPARC/CodeGen/Sanity.o
| Run Ghc CompileHs Stage1: compiler/llvmGen/LlvmCodeGen/Base.hs => _build/stage1/compiler/build/LlvmCodeGen/Base.o
| Run Ghc CompileHs Stage1: compiler/simplStg/SimplStg.hs => _build/stage1/compiler/build/SimplStg.o
| Run Ghc CompileHs Stage1: compiler/nativeGen/SPARC/CodeGen/Gen32.hs-boot => _build/stage1/compiler/build/SPARC/CodeGen/Gen32.o-boot
hadrian: getProcessGroupIDOf: does not exist (No such process)
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: _build/stage1/lib/package.conf.d/ghc-8.11.0.20191227.conf
  at need, called at src/Rules/Register.hs:113:5 in main:Rules.Register
* Depends on: _build/stage1/compiler/build/libHSghc-8.11.0.20191227-ghc8.11.0.20191227.dylib
  at need, called at src/Rules/Library.hs:146:5 in main:Rules.Library
* Depends on: _build/stage1/compiler/build/MkIface.dyn_o
  at &%>, called at src/Rules/Compile.hs:54:7 in main:Rules.Compile
* Depends on: _build/stage1/compiler/build/MkIface.dyn_o _build/stage1/compiler/build/MkIface.dyn_hi
  at error, called at src/Development/Shake/Internal/Rules/Files.hs:245:13 in shk-0.18.3-5a796314:Development.Shake.Internal.Rules.Files
* Raised the exception:
Error, &%> rule failed to produce 1 file (out of 2)
  _build/stage1/compiler/build/MkIface.dyn_o
  _build/stage1/compiler/build/MkIface.dyn_hi - MISSING

Expected behavior

builds to work :) What do you expect the reproducer described above to do? NO CLUE, race conditions are the worse

Environment

• GHC version used: 8.6.5

Optional:

• Operating System: OSX
• System Architecture: