Set compiler flags to reduce android binary size.

platforms/android/scripts/build.cmd

@@ -90,6 +90,7 @@ echo on
 %ANDROID_TOOLCHAIN_CMAKE% ^
 -DCMAKE_MAKE_PROGRAM="%MAKE%" %* "%SOURCE_DIR%" ^
 -DOPENCV_EXTRA_MODULES_PATH="%SOURCE_DIR%\opencv_contrib\modules" ^
+-DENABLE_THIN_LTO:BOOL=ON ^
 -DBUILD_SHARED_LIBS:BOOL=OFF ^
 -DBUILD_ANDROID_EXAMPLES:BOOL=OFF ^
 -DBUILD_PERF_TESTS:BOOL=OFF ^
@@ -107,9 +108,11 @@ echo on
 -DWITH_OPENCL:BOOL=ON ^
 -DWITH_CUDA:BOOL=OFF ^
 -DBUILD_ANDROID_PROJECTS=OFF ^
--DCMAKE_C_FLAGS:STRING=-std=c11 ^
--DCMAKE_CONFIGURATION_TYPES:STRING=Release) ^
+-DCMAKE_C_FLAGS:STRING="-std=c11 -fvisibility=hidden -fvisibility-inlines-hidden -flto" ^
+-DCMAKE_CXX_FLAGS:STRING="-fvisibility=hidden -fvisibility-inlines-hidden -flto" ^
+-DCMAKE_BUILD_TYPE:STRING=RELEASE) ^
 && GOTO cmakefin
+REM -DCMAKE_BUILD_TYPE:STRING=MINSIZEREL) ^
 REM -DANDROID_STL:STRING=c++_static ^
 REM -DCMAKE_CXX_FLAGS:STRING="-D__cplusplus=201103L" ^