Add aconfig_declarations for flags in android_core_networking

Add aconfig_declarations so that platform code can use this flag.
Following CLs(aosp/2606670) use this flag to sync the mainline behavior
change and platform behavior change.
Having merged-in to avoid being merged to udc-mainline-prod where
aconfig soong targets are not supported

Bug: 267870186
Test: TH
(cherry picked from https://android-review.googlesource.com/q/commit:e63d38ff37de1001ea4c851fe3512f1137dcca4d)
Merged-In: I2260dc3d60689da9328fe4f98c3f3048d96bbf6d
Change-Id: I2260dc3d60689da9328fe4f98c3f3048d96bbf6d
diff --git a/common/Android.bp b/common/Android.bp
index e10ede8..c982431 100644
--- a/common/Android.bp
+++ b/common/Android.bp
@@ -19,6 +19,8 @@
     default_applicable_licenses: ["Android-Apache-2.0"],
 }
 
+build = ["TrunkStable.bp"]
+
 // This is a placeholder comment to avoid merge conflicts
 // as the above target may not exist
 // depending on the branch