Bug 1712329: Copy DLLs to test directory for MSIX tests r=jmaher

We can't copy certutil.exe into the appdir for MSIX, so we have to do pull its dependencies out instead.

Differential Revision: https://phabricator.services.mozilla.com/D164080

testing/mochitest/runtests.py

@@ -2046,6 +2046,16 @@ toolbar#nav-bar {
             # desktop seems to use the old
             certdbPath = options.profilePath
 
+        # certutil.exe depends on some DLLs in the app directory
+        # When running tests against an MSIX-installed Firefox, these DLLs
+        # cannot be used out of the install directory, they must be copied
+        # elsewhere first.
+        if "WindowsApps" in options.app:
+            install_dir = os.path.dirname(options.app)
+            for f in os.listdir(install_dir):
+                if f.endswith(".dll"):
+                    shutil.copy(os.path.join(install_dir, f), options.utilityPath)
+
         status = call(
             [certutil, "-N", "-d", certdbPath, "-f", pwfilePath], env=toolsEnv
         )