Bug 1390964 - Do not clobber an existing LD_LIBRARY_PATH in the mochitest harness. r=ted

MozReview-Commit-ID: 7uQ71Jpq1lM

--HG--
extra : rebase_source : 451b8117427609f9528ed6549937d5be817e6e53

testing/mochitest/runtests.py

@@ -417,7 +417,10 @@ class MochitestServer(object):
         # get testing environment
         env = test_environment(xrePath=self._xrePath, log=self._log)
         env["XPCOM_DEBUG_BREAK"] = "warn"
-        env["LD_LIBRARY_PATH"] = self._xrePath
+        if not "LD_LIBRARY_PATH" in env or env["LD_LIBRARY_PATH"] is None:
+            env["LD_LIBRARY_PATH"] = self._xrePath
+        else:
+            env["LD_LIBRARY_PATH"] = ":".join([self._xrePath, env["LD_LIBRARY_PATH"]])
 
         # When running with an ASan build, our xpcshell server will also be ASan-enabled,
         # thus consuming too much resources when running together with the browser on