Bug 1686256 - Add Windows friendly wrapper for mach r=mhentges,firefox-build-system-reviewers,dmajor

This allows running mach on PowerShell for better Windows build experience. It currently has a limitation that blocks any whitespace use but such use should be rare enough.

Differential Revision: https://phabricator.services.mozilla.com/D101673

mach.ps1

@@ -0,0 +1,29 @@
+if (-not (test-path env:MOZILLABUILD)) {
+  echo "No MOZILLABUILD environment variable found, terminating."
+  exit 1
+}
+
+$mypath = $MyInvocation.MyCommand.Path
+$machpath = ($mypath -replace '\\', '/').substring(0, $mypath.length - 4)
+
+if ($machpath.contains(' ')) {
+  echo @'
+The repository path contains whitespace which currently isn't supported in mach.ps1.
+Please run MozillaBuild manually for now.
+'@
+  exit 1
+}
+
+for ($i = 0; $i -lt $args.length; $i++) {
+  $arg = $args[$i]
+  if ($arg.contains(' ')) {
+    echo @'
+The command contains whitespace which currently isn't supported in mach.ps1.
+Please run MozillaBuild manually for now.
+'@
+    exit 1
+  }
+}
+
+& "$env:MOZILLABUILD/start-shell.bat" $machpath $args
+exit $lastexitcode