Nushell: Parse Error when command argument contains equal sign

[cdhunt]

I'm trying to pass an argument to terraform and the argument syntax uses = which appears to trip up nu.

```
error: Parse Error

• shell:1:23
  1 | terraform init -backend=false
  | ^^^^^^
  ```

[wycats]

I'm starting to suspect that we need to parse external commands differently than internal commands.

We already have a hard requirement that commands are separated by |, so maybe we need a really simple tokenization step first that pulls apart the commands and then parse external commands with something like shellwords?

[cdhunt]

I would also assume I could use $it in the external command argument.

[jankoprowski]

Same with make test TESTS=my_test

[jonathandturner]

Recently @wycats landed some changes to external command support in the parser. It seems this is now fixed.

I'll close the issue, but please re-open if the issue is still happening with the latest code in master.