Bug 1536179 - cast the PosixPath to a string r=jgilbert

Changes:

Silence the `os.chdir` posixpath error when run in python3.

Differential Revision: https://phabricator.services.mozilla.com/D59254

--HG--
extra : moz-landing-system : lando

dom/canvas/test/webgl-conf/generate-wrappers-and-manifest.py

@@ -539,7 +539,7 @@ def GetFilePathListForDir(baseDir):
 
 if __name__ == '__main__':
     file_dir = Path(__file__).parent
-    os.chdir(file_dir)
+    os.chdir(str(file_dir))
 
     testEntryList = GetTestList()
     wrapperPathStrList = WriteWrappers(testEntryList)