Pass extra env variables also to the symbolizer script.

In particular LLVM_SYMBOLIZER_PATH is needed by asan_symbolize.py.

Also explicitly wait for test launcher to finish running and use its return
code as an overall exit code of the test. asan_symbolize.py always returns
0 (if it doesn't crash), not very useful.

BUG=424280
R=earthdok@chromium.org

Review URL: https://codereview.chromium.org/639713009

Cr-Commit-Position: refs/heads/master@{#300252}

testing/test_env.py

@@ -174,10 +174,11 @@ def run_executable(cmd, env):
       p1 = subprocess.Popen(cmd, env=env, stdout=subprocess.PIPE,
                             stderr=sys.stdout)
       p2 = subprocess.Popen(["../tools/valgrind/asan/asan_symbolize.py"],
-                            stdin=p1.stdout)
+                            env=env, stdin=p1.stdout)
       p1.stdout.close()  # Allow p1 to receive a SIGPIPE if p2 exits.
+      p1.wait()
       p2.wait()
-      return p2.returncode
+      return p1.returncode
     else:
       return subprocess.call(cmd, env=env)
   except OSError: