sysroot in cmakelist

cmake_sysroot_add

# Check for sysroot override via TARGET_SYSROOT environment variable.
if (DEFINED ENV{TARGET_SYSROOT})
    set(TARGET_SYSROOT "$ENV{TARGET_SYSROOT}")
    message("Target sysroot overridden by TARGET_SYSROOT environment variable")
else()
    # Ask the compiler for its sysroot.
    if(NOT USE_CLANG EQUAL 1)
        execute_process(
            COMMAND ${TARGET_CC} --print-sysroot
            OUTPUT_VARIABLE TARGET_SYSROOT
            OUTPUT_STRIP_TRAILING_WHITESPACE
        )
    endif()
endif()

message("Target sysroot: ${TARGET_SYSROOT}")

SET(CMAKE_REQUIRED_FLAGS "--sysroot=${TARGET_SYSROOT}")
add_definitions(--sysroot=${TARGET_SYSROOT})
SET(CMAKE_EXE_LINKER_FLAGS "--sysroot=${TARGET_SYSROOT}" CACHE STRING "" FORCE)
SET(CMAKE_SHARED_LINKER_FLAGS "--sysroot=${TARGET_SYSROOT}" CACHE STRING "" FORCE)
SET(CMAKE_MODULE_LINKER_FLAGS "--sysroot=${TARGET_SYSROOT}" CACHE STRING "" FORCE)

set(CMAKE_FIND_ROOT_PATH "${TARGET_SYSROOT}")
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)