With flags:
flags:
  accelerate-fft:
#    llvm-ptx: false
    llvm-cpu: false
  accelerate-examples:
#    llvm-ptx: false
    llvm-cpu: false

roger@roger-kubuntu-18lts:~/Downloads/accelerate-examples$ stack build
accelerate-fft-1.3.0.0: unregistering (missing dependencies: accelerate-llvm-ptx)
accelerate-llvm-ptx-1.3.0.0: build (lib)
Progress 1/3

--  While building package accelerate-llvm-ptx-1.3.0.0 using:
      /home/roger/.stack/setup-exe-cache/x86_64-linux-tinfo6/Cabal-simple_mPHDZzAJ_2.4.0.1_ghc-8.6.4 --builddir=.stack-work/dist/x86_64-linux-tinfo6/Cabal-2.4.0.1 build lib:accelerate-llvm-ptx --ghc-options " -ddump-hi -ddump-to-file -fdiagnostics-color=always"
    Process exited with code: ExitFailure 1
    Logs have been written to: /home/roger/Downloads/accelerate-examples/.stack-work/logs/accelerate-llvm-ptx-1.3.0.0.log

    Preprocessing library for accelerate-llvm-ptx-1.3.0.0..
    Building library for accelerate-llvm-ptx-1.3.0.0..
    [ 9 of 44] Compiling Data.Array.Accelerate.LLVM.PTX.Execute.Event[boot] ( src/Data/Array/Accelerate/LLVM/PTX/Execute/Event.hs-boot, .stack-work/dist/x86_64-linux-tinfo6/Cabal-2.4.0.1/build/Data/Array/Accelerate/LLVM/PTX/Execute/Event.o-boot )
    [11 of 44] Compiling Data.Array.Accelerate.LLVM.PTX.Target ( src/Data/Array/Accelerate/LLVM/PTX/Target.hs, .stack-work/dist/x86_64-linux-tinfo6/Cabal-2.4.0.1/build/Data/Array/Accelerate/LLVM/PTX/Target.o )
    <command line>: can't load .so/.DLL for: /home/roger/Downloads/accelerate-examples/.stack-work/install/x86_64-linux-tinfo6/lts-13.12/8.6.4/lib/x86_64-linux-ghc-8.6.4/libHSnvvm-0.9.0.0-CGS0bVdmfznJDX2QhVMRGJ-ghc8.6.4.so (libnvvm.so.3: cannot open shared object file: No such file or directory)


with flags:
#flags:
#  accelerate-fft:
#    llvm-ptx: false
#    llvm-cpu: false
#  accelerate-examples:
#    llvm-ptx: false
#    llvm-cpu: false

roger@roger-kubuntu-18lts:~/Downloads/accelerate-examples$ stack build
accelerate-llvm-ptx-1.3.0.0: build (lib)
Progress 1/3

--  While building package accelerate-llvm-ptx-1.3.0.0 using:
      /home/roger/.stack/setup-exe-cache/x86_64-linux-tinfo6/Cabal-simple_mPHDZzAJ_2.4.0.1_ghc-8.6.4 --builddir=.stack-work/dist/x86_64-linux-tinfo6/Cabal-2.4.0.1 build lib:accelerate-llvm-ptx --ghc-options " -ddump-hi -ddump-to-file -fdiagnostics-color=always"
    Process exited with code: ExitFailure 1
    Logs have been written to: /home/roger/Downloads/accelerate-examples/.stack-work/logs/accelerate-llvm-ptx-1.3.0.0.log

    Preprocessing library for accelerate-llvm-ptx-1.3.0.0..
    Building library for accelerate-llvm-ptx-1.3.0.0..
    [ 9 of 44] Compiling Data.Array.Accelerate.LLVM.PTX.Execute.Event[boot] ( src/Data/Array/Accelerate/LLVM/PTX/Execute/Event.hs-boot, .stack-work/dist/x86_64-linux-tinfo6/Cabal-2.4.0.1/build/Data/Array/Accelerate/LLVM/PTX/Execute/Event.o-boot )
    [11 of 44] Compiling Data.Array.Accelerate.LLVM.PTX.Target ( src/Data/Array/Accelerate/LLVM/PTX/Target.hs, .stack-work/dist/x86_64-linux-tinfo6/Cabal-2.4.0.1/build/Data/Array/Accelerate/LLVM/PTX/Target.o )
    <command line>: can't load .so/.DLL for: /home/roger/Downloads/accelerate-examples/.stack-work/install/x86_64-linux-tinfo6/lts-13.12/8.6.4/lib/x86_64-linux-ghc-8.6.4/libHSnvvm-0.9.0.0-CGS0bVdmfznJDX2QhVMRGJ-ghc8.6.4.so (libnvvm.so.3: cannot open shared object file: No such file or directory)