flutter: android: Fix CMakeList.txt lost

Lost when rename flutter dir to flutter_app.

src/ui/flutter_app/android/app/CMakeLists.txt

@@ -0,0 +1,52 @@
+cmake_minimum_required(VERSION 3.4.1)
+
+add_definitions(-g -O2 -std=c++17 -D FLUTTER_UI)
+
+add_library( # Sets the name of the library.
+        engine
+
+        # Sets the library as a shared library.
+        SHARED
+
+        # Provides a relative path to your source file(s).
+        src/main/cpp/mill_engine.cpp
+        ../../command/command_channel.cpp
+        ../../command/command_queue.cpp
+        ../../command/engine_main.cpp
+        ../../../../bitboard.cpp
+        ../../../../endgame.cpp
+        ../../../../evaluate.cpp
+        ../../../../main.cpp
+        ../../../../mills.cpp
+        ../../../../misc.cpp
+        ../../../../movegen.cpp
+        ../../../../movepick.cpp
+        ../../../../option.cpp
+        ../../../../position.cpp
+        ../../../../rule.cpp
+        ../../../../search.cpp
+        ../../../../thread.cpp
+        ../../../../tt.cpp
+        ../../../../uci.cpp
+        ../../../../ucioption.cpp)
+
+include_directories(
+        ../../command
+        ../../../../../include
+        ../../../../
+)
+
+find_library( # Sets the name of the path variable.
+        log-lib
+
+        # Specifies the name of the NDK library that
+        # you want CMake to locate.
+        log)
+
+
+target_link_libraries( # Specifies the target library.
+        engine
+
+        # Links the target library to the log library
+        # included in the NDK.
+        ${log-lib})