nextpnr: fix version display

    ++ (lib.optional enableGui qtbase)

    ++ (lib.optional stdenv.cc.isClang llvmPackages.openmp);

  cmakeFlags =

    [ "-DCURRENT_GIT_VERSION=${lib.substring 0 7 (lib.elemAt srcs 0).rev}"

  cmakeFlags = let

    # the specified version must always start with "nextpnr-", so add it if

    # missing (e.g. if the user overrides with a git hash)

    rev = main_src.rev;

    version = if (lib.hasPrefix "nextpnr-" rev) then rev else "nextpnr-${rev}";

  in ["-DCURRENT_GIT_VERSION=${version}"

      "-DARCH=generic;ice40;ecp5;gowin;himbaechel"

      "-DBUILD_TESTS=ON"

      "-DICESTORM_INSTALL_PREFIX=${icestorm}"