发现是drmsigntool没有编译进去，于是cd build/tools/drmsigntool/，然后mm -B，再回到源码根目录下make otapackage，然后看到如下错误：
Traceback (most recent call last):
File "./build/tools/releasetools/ota_from_target_files", line 1577, in
main(sys.argv[1:])
File "./build/tools/releasetools/ota_from_target_files", line 1534, in main
WriteFullOTAPackage(input_zip, output_zip)
File "./build/tools/releasetools/ota_from_target_files", line 493, in WriteFullOTAPackage
info_dict=OPTIONS.info_dict)
File "/home/guochongxin/rk/rk3288_5.1/build/tools/releasetools/common.py", line 883, in init
self.module = imp.load_module("device_specific", info)
File "/tmp/targetfiles-JetnRt/META/releasetools.py", line 138
try:
^
IndentationError: unindent does not match any outer indentation level
make: ** [out/target/product/rk3288/rk3288-ota-eng.guochongxin.zip] Error 1
后来发现是在device/rockchip/common/releasetools.py里面有个try的缩进不对导致。