ncnn/toolchains/aarch64-linux-gnu.toolchain.cmake

# set cross-compiled system type, it's better not use the type which cmake cannot recognized.
SET ( CMAKE_SYSTEM_NAME Linux )
SET ( CMAKE_SYSTEM_PROCESSOR aarch64 )
# for the reason of aarch64-linux-gnu-gcc DONOT need to be installed, make sure aarch64-linux-gnu-gcc and aarch64-linux-gnu-g++ can be found in $PATH: 
SET ( CMAKE_C_COMPILER "aarch64-linux-gnu-gcc" )
SET ( CMAKE_CXX_COMPILER "aarch64-linux-gnu-g++" )

# set searching rules for cross-compiler
SET ( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER )
SET ( CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY )
SET ( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY )

# set ${CMAKE_C_FLAGS} and ${CMAKE_CXX_FLAGS}flag for cross-compiled process
SET ( CMAKE_CXX_FLAGS "-std=c++11 -march=armv8-a -fopenmp ${CMAKE_CXX_FLAGS}" )

# other settings
add_definitions(-D__ARM_NEON)
add_definitions(-D__ANDROID__)
SET ( ANDROID true)