$  readelf -d _build
Dynamic section at offset 0x106c8 contains 33 entries:
  Tag                Type           Name/Value
  0x000000000000001d (RUNPATH)      Library runpath: [$ORIGIN/netcoredeps]
  0x0000000000000001 (NEEDED)       Shared library: [libpthread.so.0]
  0x0000000000000001 (NEEDED)       Shared library: [libdl.so.2]
  0x0000000000000001 (NEEDED)       Shared library: [libstdc++.so.6]
  0x0000000000000001 (NEEDED)       Shared library: [libm.so.6]
  0x0000000000000001 (NEEDED)       Shared library: [libgcc_s.so.1]
  0x0000000000000001 (NEEDED)       Shared library: [libc.so.6]
  0x000000000000001e (FLAGS)        BIND_NOW
  0x000000006ffffffb (FLAGS_1)      NOW PIE
  0x0000000000000015 (DEBUG)        0x0
  0x0000000000000007 (RELA)         0x1ba0
  0x0000000000000008 (RELASZ)       744 (bytes)
  0x0000000000000009 (RELAENT)      24 (bytes)
  0x000000006ffffff9 (RELACOUNT)    20
  0x0000000000000017 (JMPREL)       0x1e88
  0x0000000000000002 (PLTRELSZ)     2448 (bytes)
  0x0000000000000003 (PLTGOT)       0x12928
  0x0000000000000014 (PLTREL)       RELA
  0x0000000000000006 (SYMTAB)       0x340
  0x000000000000000b (SYMENT)       24 (bytes)
  0x0000000000000005 (STRTAB)       0xfc4
  0x000000000000000a (STRSZ)        3032 (bytes)
  0x000000006ffffef5 (GNU_HASH)     0xfa8
  0x0000000000000019 (INIT_ARRAY)   0x12630
  0x000000000000001b (INIT_ARRAYSZ) 72 (bytes)
  0x000000000000001a (FINI_ARRAY)   0x12628
  0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
  0x000000000000000c (INIT)         0x10f84
  0x000000000000000d (FINI)         0x10fa0
  0x000000006ffffff0 (VERSYM)       0xda8
  0x000000006ffffffe (VERNEED)      0xe88
  0x000000006fffffff (VERNEEDNUM)   5
  0x0000000000000000 (NULL)         0x0

Here's what I'm trying out now:

preConfigure = ''
  dotnet --version > DotnetCliVersion.txt
'';
preBuild = ''
  patchShebangs --build build.sh
  for rid in $dotnetRuntimeIds; do dotnet restore --runtime "$rid" "build/_build.csproj"; done
  ./build.sh Codegen --configuration ${buildType}
'';

Build itself failed.

preConfigure = ''
  dotnet --version > DotnetCliVersion.txt
  for rid in $dotnetRuntimeIds; do dotnet restore --runtime "$rid" "build/_build.csproj"; done
'';
preBuild = ''
  patchShebangs --build build.sh
  ./build.sh Codegen --configuration ${buildType}
'';

...
Executing dotnetBuildHook
patching script interpreter paths in build.sh
build.sh: interpreter directive changed from "#!/usr/bin/env bash" to "/nix/store/q7sqwn7i6w2b67adw0bmix29pxg85x3w-bash-5.3p3/bin/bash"
GNU bash, version 5.3.3(1)-release (x86_64-pc-linux-gnu)
Microsoft (R) .NET Core SDK version 9.0.305
You must install or update .NET to run this application.

App: /build/source/build/bin/Debug/_build
Architecture: x64
Framework: 'Microsoft.NETCore.App', version '8.0.0' (x64)
.NET location: /nix/store/pkvy24cwwrsg3q3rqkhak8k6j98ns5gy-dotnet-sdk-9.0.305/share/dotnet

The following frameworks were found:
  9.0.9 at [/nix/store/pkvy24cwwrsg3q3rqkhak8k6j98ns5gy-dotnet-sdk-9.0.305/share/dotnet/shared/Microsoft.NETCore.App]

Learn more:
https://aka.ms/dotnet/app-launch-failed

To install missing framework, download:
https://aka.ms/dotnet-core-applaunch?framework=Microsoft.NETCore.App&framework_version=8.0.0&arch=x64&rid=linux-x64&os=linux

[whovian@nixos-wsl:/tmp/wat/nix/hactoolnet/source]$ runPhase buildPhase
Running phase: buildPhase
Executing dotnetBuildHook
...
/nix/store/pkvy24cwwrsg3q3rqkhak8k6j98ns5gy-dotnet-sdk-9.0.305/share/dotnet/sdk/9.0.305/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(266,5): error NETSDK1005: Assets file '/tmp/wat/nix/hactoolnet/source/src/hactoolnet/obj/project.assets.json' doesn't have a target for 'net9.0'. Ensure that restore has run and that you have included 'net9.0' in the TargetFrameworks for your project. [/tmp/wat/nix/hactoolnet/source/src/hactoolnet/hactoolnet.csproj]
    0 Warning(s)
    1 Error(s)
...

So it definitely isn't expecting net8 at all, great. Guess I'm looking deeper! 😅

Yeah it seems to be setting TargetFramework to net8.0 in build/_build.csproj so I'll need to patch that and possibly update Nuke.Common in the same csproj

<PackageReference Include="Nuke.Common" Version="8.0.0" />

Good news is that Nuke ran, but throws...

...
Building stage 2 codegen project.
23:53:31 [ERR] Target Codegen has thrown an exception
System.PlatformNotSupportedException: BinaryFormatter serialization and deserialization have been removed. See https://aka.ms/binaryformatter for more information.
   at System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph)
   at Nuke.Common.Tooling.SettingsEntityExtensions.NewInstance[T](T settingsEntity) in /_/source/Nuke.Tooling/SettingsEntity.NewInstance.cs:line 23
   at Nuke.Common.Tools.DotNet.DotNetRunSettingsExtensions.SetProjectFile[T](T toolSettings, String projectFile) in /_/source/Nuke.Common/Tools/DotNet/DotNet.Generated.cs:line 5507
   at LibHacBuild.Build.RunCodegenStage2() in /tmp/wat/nix/hactoolnet/source/build/Build.cs:line 658
   at LibHacBuild.Build.<get_Codegen>b__70_1() in /tmp/wat/nix/hactoolnet/source/build/Build.cs:line 206
   at Nuke.Common.Execution.BuildExecutor.<>c.<Execute>b__4_2(Action x) in /_/source/Nuke.Build/Execution/BuildExecutor.cs:line 119
   at System.Collections.Generic.List`1.ForEach(Action`1 action)
   at Nuke.Common.Execution.BuildExecutor.Execute(NukeBuild build, ExecutableTarget target, IReadOnlyCollection`1 previouslyExecutedTargets, Boolean failureMode) in /_/source/Nuke.Build/Execution/BuildExecutor.cs:line 119
...