Make --is-base-module action store_true

By default the option consumes the next flag, which happens to be
--native-libs=libcrashpad_handler.so for chrome modern bundle modules.

Bug: 960534
Change-Id: I09c3df3c6433a85006c7143256cec2a51e14976e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1622661
Auto-Submit: Joshua Peraza <jperaza@chromium.org>
Reviewed-by: Eric Stevenson <estevenson@chromium.org>
Commit-Queue: Eric Stevenson <estevenson@chromium.org>
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662028}
diff --git a/build/android/gyp/write_build_config.py b/build/android/gyp/write_build_config.py
index 880f2c9..2c96173 100755
--- a/build/android/gyp/write_build_config.py
+++ b/build/android/gyp/write_build_config.py
@@ -970,6 +970,7 @@
       help='Path to R.txt file for the base resources whitelist.')
   parser.add_option(
       '--is-base-module',
+      action='store_true',
       help='Specifies that this module is a base module for some app bundle.')
 
   parser.add_option('--generate-markdown-format-doc', action='store_true',