[Sanitizers] Fix lint failure with Python 3.6

There are some files in compiler-rt that use UTF-8 characters in some of the
comments. This causes lint failures with some versions of Python. This patch
just makes the encoding explicit in the call to open.

compiler-rt/lib/sanitizer_common/scripts/litlint.py

@@ -45,7 +45,7 @@ def LintFile(p):
     The number of errors detected.
   """
   errs = 0
-  with open(p, 'r') as f:
+  with open(p, 'r', encoding='utf-8') as f:
     for i, s in enumerate(f.readlines(), start=1):
       msg, col = LintLine(s)
       if msg != None: