--passNim doesn't affect *.nimble file interpretation
Nimble-0.11.0, Nim-1.0.0, Windows 10 64-bit

test1.nimble:

```nim
version       = "0.1.0"
author        = "Stefan Talpalaru"
description   = "A new awesome nimble package"
license       = "MIT"
srcDir        = "src"

requires "nim >= 1.0.0"

task foo, "bar":
  when defined(windows):
    when defined(vcc):
      echo "defined(vcc)"
    else:
      echo "not defined(vcc)"
```

`nimble --passNim:-d:vcc --debug foo`:

```text
  Executing task foo in C:\Users\user\Desktop\status\test1\test1.nimble
     Debug: Executing nim e --hints:off --verbosity:0 -p:C:\Users\user\AppData\Local\Temp\nimblecache C:\Users\user\Desktop\status\test1\test1_4840.nims C:\Users\user\AppData\Local\Temp\nimble_4840.out foo --passNim:-d:vcc
not defined(vcc)
```
Same with `nimble --passNim:--cc:vcc --debug foo` or passing the compiler flags to Nimble directly. Nothing seems to be able to "define(vcc)" in a *.nimble file.