linter: Use same Python interpreter when executing script in subprocess

If a specific Python interpreter is used (e.g. by invoking the script with
"/path/to/python run.py") then we should use the same Python interpreter
to execute scripts in subprocesses, not the one from the environment.

The path to the running Python interpreter is given by sys.executable.

tools/lint/test/run.py

@@ -18,7 +18,7 @@ class TestLinter(unittest.TestCase):
         return fspath
 
     def lint(self, args):
-        args[:0] = [ex]
+        args[:0] = [sys.executable, ex]
         sp = subprocess.Popen(args,
                               stdout=subprocess.PIPE,
                               stderr=subprocess.PIPE,