gn2bp: move jni_generator.py --prev_output_dir to sanitizer

Test: none
Change-Id: Id28d5ce912913d2a27dc5fb7aacb8021e7008028
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
index 34c0010..28513fa 100755
--- a/tools/gn2bp/gen_android_bp
+++ b/tools/gn2bp/gen_android_bp
@@ -674,7 +674,7 @@
       return
     assert(not self._is_list_arg(arg))
     hasValue = self._is_value_arg(arg)
-    i = self.target.index(arg)
+    i = self.target.args.index(arg)
     self.target.args.pop(i)
     if hasValue:
       self.target.args.pop(i)
@@ -716,6 +716,7 @@
       self._append_arg('--javap', '$$(find out/.path -name javap)')
     self._update_value_arg('--output_dir', self._sanitize_dir)
     self._update_value_arg('--includes', self._sanitize_dir)
+    self._delete_arg('--prev_output_dir')
     return super().get_args()
 
 
@@ -781,10 +782,6 @@
         # TODO: put inside function
         filename = re.sub('^\.\./\.\./', '', target.args[i + 1])
         target.args[i + 1] = '$(location %s)' % filename
-      elif val == '--prev_output_dir':
-        # this is not needed for aosp builds.
-        target.args[i] = ''
-        target.args[i + 1] = ''
       elif val == '--jar_file':
         # delete leading ../../ and add path to javap
         filename = re.sub('^\.\./\.\./', '', target.args[i + 1])