Fix the XLA disabling mechanism in configure.py

Environment variables are strings, not integers.'0' does not evaluate to false.

PiperOrigin-RevId: 297916971
Change-Id: I9df143690b16a181fa5f0c4a60ac2f944b396672
diff --git a/configure.py b/configure.py
index b93612a..f2c6e0c 100644
--- a/configure.py
+++ b/configure.py
@@ -1390,7 +1390,7 @@
   else:
     environ_cp['TF_CONFIGURE_IOS'] = '0'
 
-  if environ_cp.get('TF_ENABLE_XLA', 1):
+  if environ_cp.get('TF_ENABLE_XLA', '1') == '1':
     write_to_bazelrc('build --config=xla')
 
   set_action_env_var(