Move top-level Android.bp to under build

Bug: 352458998
Test: pass TH
Change-Id: I3c3e7848013ca62edb3cef10676878c9c0834d6d
diff --git a/Android.bp b/build/Android.bp
similarity index 100%
rename from Android.bp
rename to build/Android.bp
diff --git a/avf_flags.aconfig b/build/avf_flags.aconfig
similarity index 100%
rename from avf_flags.aconfig
rename to build/avf_flags.aconfig