test: decode the output of lldb -P as UTF-8

We currently use the byte string as the PYTHONPATH with Python 3, which
is odd.

Author: compnerd

test/lit.cfg

@@ -102,7 +102,7 @@ def get_lldb_python_path(lldb_build_root):
     lldb_path = os.path.join(lldb_build_root, 'bin', 'lldb')
     if not os.access(lldb_path, os.F_OK):
         return None
-    return subprocess.check_output([lldb_path, "-P"]).rstrip()
+    return subprocess.check_output([lldb_path, "-P"]).rstrip().decode('utf-8')
 
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