setCommand runs after the `after` block
Given a task `b` and an `after b: ...` hook, the `after` block runs before `b`. Repro:

https://gist.github.com/citycide/86ddf061c6ada8e0218edaf7119f076e

(Note that you can clone gists as git repos, `git clone https://gist.github.com/86ddf061c6ada8e0218edaf7119f076e.git`)

```nim
# nimble_tasks.nim
when isMainModule:
  echo "Hello, World!"
```

```nim
# nimble_tasks.nimble
version     = "0.1.0"
author      = "citycide"
description = "Nimble task hooks repro"
license     = "MIT"
bin         = @["nimble_tasks"]

requires "nim >= 0.19.0"

template exe (s: string): string =
  if buildOS == "windows": s & ".exe" else: s

after b:
  # this runs before the `b` task is done?
  echo existsFile("nt".exe) # -> false??

task b, "build a thing":
  rmFile "nt".exe
  switch "out", "nt".exe
  switch "define", "release"
  setCommand "c", "nimble_tasks.nim"
```

---

```
» nim -v
Nim Compiler Version 0.19.0 [Windows: amd64]
Compiled at 2018-10-03
Copyright (c) 2006-2018 by Andreas Rumpf

active boot switches: -d:release

» nimble -v
nimble v0.9.0 compiled at 2018-10-03 02:18:38
git hash: af1c1d73c32b6e9fe7a8aecf3768d9f482b18180
```