fix(setup): Fix setup.ps1 to check Get-Acl exists

* `Get-Acl` not found in Linux Powershell version, so only call it
  if it exists.

docs/src/templates/setup.ps1.mustache

@@ -58,17 +58,30 @@ catch [System.Management.Automation.CommandNotFoundException] {
 Test-Git-Config -Option "user.name" -ErrMsg "Git username not set!`nRun: git config --global user.name 'My Name'"
 Test-Git-Config -Option "user.email" -ErrMsg "Git email not set!`nRun: git config --global user.email 'example@myemail.com'"
 
-$permission = (Get-Acl $pwd).Access | 
-?{$_.IdentityReference -match $env:UserName `
-	-and $_.FileSystemRights -match "FullControl" `
-		-or $_.FileSystemRights -match "Write"	} | 
-
-		Select IdentityReference,FileSystemRights
-
-If (-Not $permission){
-    Write-Host "Sorry, you do not have write permissions in this directory."
-    Write-Host "Please try running this script again from a directory that you do have write permissions for."
-    exit 1
+function Test-CommandExists {
+    param ($command)
+
+    $oldPreference = $ErrorActionPreference
+    $ErrorActionPreference = ‘stop’
+
+    try {
+        if(Get-Command $command){ return $true }
+    } Catch { return $false }
+    Finally { $ErrorActionPreference=$oldPreference }
+}
+
+if (Test-CommandExists Get-Acl) {
+    $permission = (Get-Acl $pwd).Access |
+    ?{$_.IdentityReference -match $env:UserName `
+        -and $_.FileSystemRights -match "FullControl" `
+        -or $_.FileSystemRights -match "Write" } | 
+             Select IdentityReference,FileSystemRights
+
+    If (-Not $permission){
+        Write-Host "Sorry, you do not have write permissions in this directory."
+        Write-Host "Please try running this script again from a directory that you do have write permissions for."
+        exit 1
+    }
 }
 
 $repo_path = "https://github.com/zmkfirmware/zmk-config-split-template.git"