Fix shell setting precedence (#1306)

examples/powershell.just

@@ -0,0 +1,29 @@
+# Cross platform shebang:
+shebang := if os() == 'windows' {
+  'powershell.exe'
+} else {
+  '/usr/bin/env pwsh'
+}
+
+# Set shell for non-Windows OSs:
+set shell := ["powershell", "-c"]
+
+# Set shell for Windows OSs:
+set windows-shell := ["powershell.exe", "-NoLogo", "-Command"]
+
+# If you have PowerShell Core installed and want to use it,
+# use `pwsh.exe` instead of `powershell.exe`
+
+linewise:
+  Write-Host "Hello, world!"
+
+shebang:
+	#!{{shebang}}
+	$PSV = $PSVersionTable.PSVersion | % {"$_" -split "\." }
+	$psver = $PSV[0] + "." + $PSV[1]
+	if ($PSV[2].Length -lt 4) {
+		$psver += "." + $PSV[2] + " Core"
+	} else {
+		$psver += " Desktop"
+	}
+	echo "PowerShell $psver"