Move bazel_module property to a common file, and add it to filegroup.

This enables prototyping against aosp/1441774 to demonstrate mixed
builds with converted BUILD files.

Test: TH Presubmit
Test: USE_BAZEL_ANALYSIS=1 m libc && prebuilts/build-tools/linux-x86/bin/ninja -f out/combined-aosp_cf_x86_auto.ninja -t commands libc | grep bazel-out | wc -l # 2 build actions
Bug: 171263886

Change-Id: I7b5cd0449d043ba26a339a0ef98b562fc62e13c8
diff --git a/android/filegroup.go b/android/filegroup.go
index 68311e3..9425616 100644
--- a/android/filegroup.go
+++ b/android/filegroup.go
@@ -15,6 +15,7 @@
 package android
 
 import (
+	"android/soong/bazel"
 	"strings"
 )
 
@@ -37,6 +38,9 @@
 	// Create a make variable with the specified name that contains the list of files in the
 	// filegroup, relative to the root of the source tree.
 	Export_to_make_var *string
+
+	// Properties for Bazel migration purposes.
+	bazel.Properties
 }
 
 type fileGroup struct {