gn2bp: Add pre_create_action_module

To support //build:chromeos_buildflags
Add pre_create_action_module for target specific modification before the
create_action_module.
There might be a better way to target specific modification but this
makes //build:chromeos_buildflags specific change small for now.

Test: ./update_result.sh, m cronet_aml_base_base_static
Change-Id: I28e0758f84bebf3405298d7b908b6443914b3944
diff --git a/tools/gn2bp/update_results.sh b/tools/gn2bp/update_results.sh
index b7b880f..58f0600 100755
--- a/tools/gn2bp/update_results.sh
+++ b/tools/gn2bp/update_results.sh
@@ -14,6 +14,7 @@
 TARGETS=(
   "//third_party/zlib:zlib"
   "//third_party/libevent:libevent"
+  "//base:base_static"
 )
 
 BASEDIR=$(dirname "$0")