Move 5.1 build system to a variant

[michaelblyons]

So Windows can run either one

Fixes #204

[deathaxe]

"variants" doesn't need to be wrapped into "windows"

Suggested change

	"windows": {
	"cmd": ["powershell.exe", "-noprofile", "-ExecutionPolicy", "Bypass", "-file", "$file"],
	}
	"variants": [
	{
	"name": "Windows PowerShell (<=5.1)",
	"windows": {
	"cmd": ["powershell.exe", "-noprofile", "-ExecutionPolicy", "Bypass", "-file", "$file"],
	},
	},
	],
	},
	"variants": [
	{
	"name": "Windows PowerShell (<=5.1)",
	"windows": {
	"cmd": ["powershell.exe", "-noprofile", "-ExecutionPolicy", "Bypass", "-file", "$file"],
	}
	}
	]

[michaelblyons]

The way your version works, there's a "Windows PowerShell" build available here on Linux (but shouldn't be). I'll push a different variation and see what you think.

[deathaxe]

Then probably vice versa. What triggered me was duplicate "windows" entry, which I think may be redundant.

[michaelblyons]

Okay, I'll try it that way. What was wrong with the current state? Is the main pwsh one missing?

[deathaxe]

"variants" must be a top-level key. Hence your current revision, despite duplicating "windows" key, does not add the desired entry on Windows platform.

[deathaxe]

As it seems, platform-sepcificly visible variants are not supported.