Move common settings in BoardConfig.mk into a common makefile

Bug: 63878637
Test: Build pass and boot into home screen with aosp_arm64_ab of GSI
Change-Id: I1b843fcccd83e2e30eba66451b10f093ccfd458f
diff --git a/target/board/treble_common_64.mk b/target/board/treble_common_64.mk
new file mode 100644
index 0000000..8980dfd
--- /dev/null
+++ b/target/board/treble_common_64.mk
@@ -0,0 +1,20 @@
+#
+# Copyright (C) 2017 The Android Open-Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+include build/make/target/board/treble_common.mk
+
+# Enable 64-bits binder
+TARGET_USES_64_BIT_BINDER := true