gn2bp: fix output_dir arg for jni_generator.py

Test: m cronet_aml_base_base_jni_headers
Change-Id: I308763fa32b1fda312786f9de577159f2c21958d
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
index 85fdba5..40addef 100755
--- a/tools/gn2bp/gen_android_bp
+++ b/tools/gn2bp/gen_android_bp
@@ -682,8 +682,8 @@
 
   elif target.script == '//base/android/jni_generator/jni_generator.py':
     for i, val in enumerate(target.args):
-      if val == '--output_file':
-        # replace --output_file gen/... with --output_file $(genDir)/...
+      if val == '--output_dir':
+        # replace --output_dir gen/... with --output_dir $(genDir)/...
         target.args[i + 1] = re.sub('^gen', '$(genDir)', target.args[i + 1])
       if val == '--input_file':
         # --input_file supports both .class specifiers or source files as arguments.