fftools: Fix MediaCodec on Android15+

On Android15+ MediaCodec HAL backend was switched from HIDL to AIDL.
As a result, MediaCodec operations started to hang, see:

    https://trac.ffmpeg.org/ticket/11363
    https://github.com/termux/termux-packages/issues/21264
    https://issuetracker.google.com/issues/382831999

To fix that it is necessary to initialize binder thread pool.

Signed-off-by: Dmitrii Okunev <xaionaro@dx.center>

compat/android/binder.h

@@ -0,0 +1,31 @@
+/*
+ * Android Binder handler
+ *
+ * Copyright (c) 2025 Dmitrii Okunev
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef COMPAT_ANDROID_BINDER_H
+#define COMPAT_ANDROID_BINDER_H
+
+/**
+ * Initialize Android Binder thread pool.
+ */
+void android_binder_threadpool_init_if_required(void);
+
+#endif                          // COMPAT_ANDROID_BINDER_H