add android build scripts

engine/Scripts/full_build.sh

 done
 
 case $platform in
-    "andorid")  echo 'You select android'
+    "android")  ./lib_build_android.sh -r $engine_path $optimize -p android -m $runtime_mode
     ;;
     "ios")  ./lib_build_ios.sh -r $engine_path $optimize -p ios -m $runtime_mode $bitcode
     ;;

engine/Scripts/lib_build_android.sh

+work_path=$(pwd)
+engine_path=
+platform=
+gn_params=""
+optimize="--unoptimized"
+ninja_params=""
+runtime_mode=
+
+
+echo "setting environment variable and other params..."
+
+while getopts ":r:p:m:eo" opt
+do
+    case $opt in
+        r)
+        engine_path=$OPTARG # set engine_path, depot_tools and flutter engine folder will be put into this path
+        ;;
+        p)
+        gn_params="$gn_params --$OPTARG" # set the target platform android/ios
+        ;;
+        m)
+        runtime_mode=$OPTARG
+        gn_params="$gn_params --runtime-mode=$runtime_mode" # set runtime mode release/debug
+        ;;
+        e)
+        gn_params="$gn_params --bitcode" # enable-bitcode switch
+        ;;
+        o)
+        optimize="" # optimize code switch
+        ;;
+        ?)
+        echo "unknown param"
+        exit 1;;
+    esac
+done
+
+if [ "$runtime_mode" == "release" ] && [ "$optimize" == "--unoptimized" ];
+then
+  output_path="android_release_unopt"
+  ninja_params=" -C out/android_release_unopt flutter/third_party/txt:txt_lib"
+elif [ "$runtime_mode" == "release" ] && [ "$optimize" == "" ];
+then
+  output_path="android_release"
+  ninja_params="-C out/android_release flutter/third_party/txt:txt_lib"
+elif [ "$runtime_mode" == "debug" ] && [ "$optimize" == "--unoptimized" ];
+then
+  output_path="android_debug_unopt"
+  ninja_params=" -C out/android_debug_unopt flutter/third_party/txt:txt_lib"
+elif [ "$runtime_mode" == "debug" ] && [ "$optimize" == "" ];
+then
+  output_path="android_debug"
+  ninja_params=" -C out/android_debug flutter/third_party/txt:txt_lib"
+elif [ "$runtime_mode" == "profile" ];
+then
+  echo "not support profile build yet"
+  exit 1
+fi
+
+gn_params="$gn_params $optimize"
+
+#set environment variable
+function isexist()
+{
+    source_str=$1
+    test_str=$2
+    
+    strings=$(echo $source_str | sed 's/:/ /g')
+    for str in $strings
+    do  
+        if [ $test_str = $str ]; then
+            return 0
+        fi  
+    done
+    return 1
+}
+
+if [ ! $FLUTTER_ROOT_PATH ];then
+  echo "export FLUTTER_ROOT_PATH=$engine_path/engine/src" >> ~/.bash_profile
+else
+  echo "This environment variable has been set, skip"
+fi
+
+if isexist $PATH $engine_path/depot_tools; then 
+  echo "This environment variable has been set, skip"
+else 
+  echo "export PATH=$engine_path/depot_tools:\$PATH" >> ~/.bash_profile
+fi
+source ~/.bash_profile
+
+echo "\nGetting Depot Tools..." 
+if [ ! -n "$engine_path" ]; then   
+  echo "Flutter engine path is not exist, please set the path by using \"-r\" param to set a engine path."  
+  exit 1
+fi
+cd $engine_path	
+if [ -d 'depot_tools' ] && [ -d "depot_tools/.git" ];
+then
+  echo "depot_tools already installed, skip"
+else
+  git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
+  gclient
+fi
+
+echo "\nGetting flutter engine..."
+
+if [ -d 'engine' ];
+then
+  echo "engine folder already exist, skip"
+else
+  mkdir engine
+fi
+cd engine
+#git@github.com:guanghuispark/engine.git is a temp repo, replace it later
+echo "solutions = [
+  {
+    \"managed\": False,
+    \"name\": \"src/flutter\",
+    \"url\": \"git@github.com:guanghuispark/engine.git\", 
+    \"custom_deps\": {},
+    \"deps_file\": \"DEPS\",
+    \"safesync_url\": \"\",
+  },
+]" > .gclient
+
+gclient sync
+
+cd $FLUTTER_ROOT_PATH/flutter
+git checkout flutter-1.17-candidate.5
+gclient sync -D
+
+echo "\nSCompiling engine..."
+#apply patch to Build.gn
+cd $FLUTTER_ROOT_PATH/flutter/third_party/txt
+cp -f $work_path/patches/android/BUILD.gn.patch BUILD.gn.patch
+patch < BUILD.gn.patch -N
+
+cd $FLUTTER_ROOT_PATH/build/secondary/third_party/libcxxabi
+cp -f $work_path/patches/android/BUILD_2.gn.patch BUILD_2.gn.patch
+patch < BUILD_2.gn.patch -N
+
+cd $FLUTTER_ROOT_PATH/build/mac
+cp -f $work_path/patches/find_sdk.patch find_sdk.patch
+patch < find_sdk.patch -N
+
+cd $FLUTTER_ROOT_PATH
+./flutter/tools/gn $gn_params
+
+ninja $ninja_params
+
+echo "\nStarting build engine..."
+cd $work_path/../
+
+python $FLUTTER_ROOT_PATH/flutter/sky/tools/objcopy.py --objcopy $FLUTTER_ROOT_PATH/third_party/android_tools/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/bin/arm-linux-androideabi-objcopy --input $FLUTTER_ROOT_PATH/third_party/icu/flutter/icudtl.dat --output icudtl.o --arch arm
+
+if [ -d '../com.unity.uiwidgets/Runtime/Plugins/android' ];
+then
+  echo "android folder already exist, skip create folder"
+else
+  mkdir ../com.unity.uiwidgets/Runtime/Plugins/android
+fi
+
+if [ "$runtime_mode" == "release" ];
+then
+  mono bee.exe android_release
+  rm -rf ../com.unity.uiwidgets/Runtime/Plugins/android/libUIWidgets.so
+  cp -r build_release/. ../com.unity.uiwidgets/Runtime/Plugins/android
+elif [ "$runtime_mode" == "debug" ];
+then
+  mono bee.exe android_debug
+  rm -rf ../com.unity.uiwidgets/Runtime/Plugins/android/libUIWidgets.so
+  cp -r build_release/. ../com.unity.uiwidgets/Runtime/Plugins/android
+fi
+
+cd $work_path/../artifacts/rsp
+cp -f $work_path/patches/android/rsp.patch rsp.patch
+patch < rsp.patch -N
+
+cd $work_path/../
+"artifacts/Stevedore/android-ndk-mac/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang++" @"artifacts/rsp/14590475716575637239.rsp"
+$FLUTTER_ROOT_PATH/buildtools/mac-x64/clang/bin/clang++ @"artifacts/rsp/14590475716575637239.rsp"
+cp artifacts/libUIWidgets/release_Android_arm32/libUIWidgets.so ../com.unity.uiwidgets/Runtime/Plugins/Android/libUIWidgets.so 
+

engine/Scripts/patches/android/BUILD.gn.patch

+--- /Users/unity/Documents/GitHub/EngineBuildTool/engine/src/flutter/third_party/txt/BUILD.gn	2021-05-19 11:45:24.000000000 +0800
++++ /Users/unity/Documents/GitHub/EngineBuildTool/engine/src/flutter/third_party/txt/modify/BUILD.gn	2021-05-19 11:44:06.000000000 +0800
+@@ -141,6 +141,9 @@
+     "//third_party/harfbuzz",
+     "//third_party/icu",
+     "//third_party/skia",
++    "//third_party/skia/modules/skottie",
++    "//third_party/libcxx",
++    "//third_party/libcxxabi",
+   ]
+ 
+   deps = [
+@@ -339,3 +342,10 @@
+     deps += [ "//third_party/skia/modules/skparagraph" ]
+   }
+ }
++
++static_library("txt_lib") {
++  complete_static_lib = true
++  deps = [
++    ":txt",
++  ]
++}

engine/Scripts/patches/android/BUILD_2.gn.patch

+--- /Users/unity/Documents/GitHub/EngineBuildTool/engine/src/build/secondary/third_party/libcxxabi/BUILD.gn	2021-05-19 10:57:31.000000000 +0800
++++ /Users/unity/Documents/GitHub/EngineBuildTool/engine/src/build/secondary/third_party/libcxxabi/modify/BUILD.gn	2021-05-19 11:53:06.000000000 +0800
+@@ -7,7 +7,6 @@
+ }
+ 
+ source_set("libcxxabi") {
+-  visibility = [ "../libcxx:*" ]
+ 
+   sources = [
+     "src/abort_message.cpp",