一步步都是按照官網的要求做的，ubuntu的版本是16.04LTS 64bit

make -j4

"

============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=7.1.1
TARGET_PRODUCT=aosp_arm64
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_ARCH=arm64
TARGET_ARCH_VARIANT=armv8-a
TARGET_CPU_VARIANT=generic
TARGET_2ND_ARCH=arm
TARGET_2ND_ARCH_VARIANT=armv7-a-neon
TARGET_2ND_CPU_VARIANT=cortex-a15
HOST_ARCH=x86_64
HOST_2ND_ARCH=x86
HOST_OS=linux
HOST_OS_EXTRA=Linux-4.8.0-39-generic-x86_64-with-Ubuntu-16.04-xenial
HOST_CROSS_OS=windows
HOST_CROSS_ARCH=x86
HOST_CROSS_2ND_ARCH=x86_64
HOST_BUILD_TYPE=release
BUILD_ID=NYC
OUT_DIR=out
============================================"

Error:

“

[ 96% 25/26] glob external/*/Android.bp
[  0% 1/46910] build out/target/product/generic_arm64/obj/ETC/file_contexts.bin_intermediates/file_contexts.local.tmp
FAILED: out/target/product/generic_arm64/obj/ETC/file_contexts.bin_intermediates/file_contexts.local.tmp
/bin/bash -c "m4 -s system/sepolicy/private/file_contexts out/target/product/generic_arm64/obj/ETC/sectxfile_nl_intermediates/sectxfile_nl > out/target/product/generic_arm64/obj/ETC/file_contexts.bin_intermediates/file_contexts.local.tmp"
/bin/bash: m4: command not found
[  0% 2/46910] build out/target/product/generic_arm64/obj/ETC/file_contexts.bin_intermediates/file_contexts.device.tmp
FAILED: out/target/product/generic_arm64/obj/ETC/file_contexts.bin_intermediates/file_contexts.device.tmp
/bin/bash -c "m4 -s  system/sepolicy/vendor/file_contexts out/target/product/generic_arm64/obj/ETC/sectxfile_nl_intermediates/sectxfile_nl build/target/board/generic/sepolicy/file_contexts > out/target/product/generic_arm64/obj/ETC/file_contexts.bin_intermediates/file_contexts.device.tmp"
/bin/bash: m4: command not found
[  0% 3/46910] Target buildinfo: out/target/product/generic_arm64/obj/ETC/system_build_prop_intermediates/build.prop
Target buildinfo from: build/target/board/generic_arm64/system.prop
[  0% 4/46910] target StaticLib: libtrunks_test (out/target/product/gen...m64/obj/STATIC_LIBRARIES/libtrunks_test_intermediates/libtrunks_test.a
ninja: build stopped: subcommand failed.
20:38:09 ninja failed with: exit status 1
build/core/main.mk:24: recipe for target 'run_soong_ui' failed
make: *** [run_soong_ui] Error 1


#### make failed to build some targets (28:58 (mm:ss)) ####

”

What's the fuck? How to solve it???