Export TARGET_ENABLE_MEDIADRM_64 to Soong.

The change enables conversion of
hardware/interfaces/drm/1.0/default from make to Soong
by exporting a variable used in a conditional check by
the modules in that directory.

Bug: 161571531
Bug: 123557988
Test: Build with TARGET_ENABLE_MEDIADRM_64 :=
Test: Build with TARGET_ENABLE_MEDIADRM_64 := true
Test: Insepction of out/soong/soong.variables for each
Test: Inspection of target files package for each
Test: Verify inclusion of modules in vendor snapshot
Change-Id: I5737d9d4687e182595a213be000b2e56c7536b8a
diff --git a/core/android_soong_config_vars.mk b/core/android_soong_config_vars.mk
new file mode 100644
index 0000000..ee12c8c
--- /dev/null
+++ b/core/android_soong_config_vars.mk
@@ -0,0 +1,29 @@
+# Copyright (C) 2020 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.
+
+# This file defines the Soong Config Variable namespace ANDROID, and also any
+# variables in that namespace.
+
+# The expectation is that no vendor should be using the ANDROID namespace. This
+# check ensures that we don't collide with any existing vendor usage.
+
+ifdef SOONG_CONFIG_ANDROID
+$(error The Soong config namespace ANDROID is reserved.)
+endif
+
+$(call add_soong_config_namespace,ANDROID)
+
+# Add variables to the namespace below:
+
+$(call add_soong_config_var,ANDROID,TARGET_ENABLE_MEDIADRM_64)
diff --git a/core/config.mk b/core/config.mk
index b928af0..7244b9f 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -1227,6 +1227,7 @@
     product-graph dump-products
 
 ifeq ($(CALLED_FROM_SETUP),true)
+include $(BUILD_SYSTEM)/android_soong_config_vars.mk
 include $(BUILD_SYSTEM)/ninja_config.mk
 include $(BUILD_SYSTEM)/soong_config.mk
 endif