transcoding: use __ANDROID_API_FUTURE__ in __builtin_available check

__builtin_available 31 fails because we're not officially 31 yet.
Use __ANDROID_API_FUTURE__ for now.

bug: 178144708
test: builds; transcoding unit tests; manually test transcoding works.
Change-Id: I4ccf05f3858feb9e22eb294b4443edc830737204
diff --git a/media/libmediatranscoding/TranscodingClientManager.cpp b/media/libmediatranscoding/TranscodingClientManager.cpp
index 09afb1f..87c984e 100644
--- a/media/libmediatranscoding/TranscodingClientManager.cpp
+++ b/media/libmediatranscoding/TranscodingClientManager.cpp
@@ -302,7 +302,7 @@
     }
 
     int32_t result;
-    if (__builtin_available(android 31, *)) {
+    if (__builtin_available(android __TRANSCODING_MIN_API__, *)) {
         if (APermissionManager_checkPermission("android.permission.WRITE_MEDIA_STORAGE", pid, uid,
                                                &result) == PERMISSION_MANAGER_STATUS_OK &&
             result == PERMISSION_MANAGER_PERMISSION_GRANTED) {
diff --git a/media/libmediatranscoding/TranscodingUidPolicy.cpp b/media/libmediatranscoding/TranscodingUidPolicy.cpp
index b0fa545..feaecc6 100644
--- a/media/libmediatranscoding/TranscodingUidPolicy.cpp
+++ b/media/libmediatranscoding/TranscodingUidPolicy.cpp
@@ -48,7 +48,7 @@
 }
 
 void TranscodingUidPolicy::registerSelf() {
-    if (__builtin_available(android 31, *)) {
+    if (__builtin_available(android __TRANSCODING_MIN_API__, *)) {
         mUidObserver = AActivityManager_addUidImportanceListener(&OnUidImportance, -1, (void*)this);
     }
 
@@ -63,7 +63,7 @@
 }
 
 void TranscodingUidPolicy::unregisterSelf() {
-    if (__builtin_available(android 31, *)) {
+    if (__builtin_available(android __TRANSCODING_MIN_API__, *)) {
         AActivityManager_removeUidImportanceListener(mUidObserver);
         mUidObserver = nullptr;
 
@@ -91,7 +91,7 @@
     }
 
     int32_t state = IMPORTANCE_UNKNOWN;
-    if (__builtin_available(android 31, *)) {
+    if (__builtin_available(android __TRANSCODING_MIN_API__, *)) {
         if (mRegistered && AActivityManager_isUidActive(uid)) {
             state = AActivityManager_getUidImportance(uid);
         }
diff --git a/media/libmediatranscoding/include/media/TranscodingUidPolicy.h b/media/libmediatranscoding/include/media/TranscodingUidPolicy.h
index 4dde5a6..dcb22df 100644
--- a/media/libmediatranscoding/include/media/TranscodingUidPolicy.h
+++ b/media/libmediatranscoding/include/media/TranscodingUidPolicy.h
@@ -28,6 +28,9 @@
 #include <unordered_map>
 #include <unordered_set>
 
+// TODO: replace __ANDROID_API_FUTURE__with 31 when it's official (b/178144708)
+#define __TRANSCODING_MIN_API__ __ANDROID_API_FUTURE__
+
 struct AActivityManager_UidImportanceListener;
 
 namespace android {