Fix build for Apple M1 when running PowerShell 7.2 (arm64)

The previous fix assumed PowerShell was always running in an emulated
mode (i.e. running PowerShell (x64) but on an Apple M1). Now that
PowerShell 7.2 has a native build for Apple M1 (arm64) the check needs
to handle both cases.

We must also skip asking `dotnet-install` to install the 3.1 or 5.0 .NET
Runtimes on an Apple M1 because they don't exist, but their installer
tries to get them anyway. This was a non-breaking bug previously where
the macOS x64 runtimes would be installed, but not used.

Author: andyleejordan

PowerShellEditorServices.build.ps1

@@ -29,7 +29,9 @@ $script:dotnetTestArgs = @(
 )
 
 $script:IsNix = $IsLinux -or $IsMacOS
-$script:IsRosetta = $IsMacOS -and (sysctl -n sysctl.proc_translated) -eq 1 # Mac M1
+# For Apple M1, pwsh might be getting emulated, in which case we need to check
+# for the proc_translated flag, otherwise we can check the architecture.
+$script:IsAppleM1 = $IsMacOS -and ((sysctl -n sysctl.proc_translated) -eq 1 -or (uname -m) -eq "arm64")
 $script:BuildInfoPath = [System.IO.Path]::Combine($PSScriptRoot, "src", "PowerShellEditorServices.Hosting", "BuildInfo.cs")
 $script:PsesCommonProps = [xml](Get-Content -Raw "$PSScriptRoot/PowerShellEditorServices.Common.props")
 
@@ -110,8 +112,12 @@ task SetupDotNet -Before Clean, Build, TestServerWinPS, TestServerPS7, TestServe
 
     if (!(Test-Path $dotnetExePath)) {
         # TODO: Test .NET 5 with PowerShell 7.1
+        #
+        # We use the .NET 6 SDK, so we always install it and its runtime.
         Install-Dotnet -Channel '6.0' # SDK and runtime
-        Install-Dotnet -Channel '3.1','5.0' -Runtime # Runtime only
+        # Anywhere other than on a Mac with an M1 processor, we additionally
+        # install the .NET 3.1 and 5.0 runtimes (but not their SDKs).
+        if (!$script:IsAppleM1) { Install-Dotnet -Channel '3.1','5.0' -Runtime }
     }
 
     # This variable is used internally by 'dotnet' to know where it's installed
@@ -235,7 +241,7 @@ task TestServerWinPS -If (-not $script:IsNix) {
     exec { & $script:dotnetExe $script:dotnetTestArgs $script:NetRuntime.Desktop }
 }
 
-task TestServerPS7 -If (-not $script:IsRosetta) {
+task TestServerPS7 -If (-not $script:IsAppleM1) {
     Set-Location .\test\PowerShellEditorServices.Test\
     exec { & $script:dotnetExe $script:dotnetTestArgs $script:NetRuntime.PS7 }
 }
@@ -249,7 +255,7 @@ task TestE2E {
     Set-Location .\test\PowerShellEditorServices.Test.E2E\
 
     $env:PWSH_EXE_NAME = if ($IsCoreCLR) { "pwsh" } else { "powershell" }
-    $NetRuntime = if ($IsRosetta) { $script:NetRuntime.PS72 } else { $script:NetRuntime.PS7 }
+    $NetRuntime = if ($IsAppleM1) { $script:NetRuntime.PS72 } else { $script:NetRuntime.PS7 }
     exec { & $script:dotnetExe $script:dotnetTestArgs $NetRuntime }
 
     # Run E2E tests in ConstrainedLanguage mode.