Sdk: Couldn't find the gn binary at path "dart-sdk/buildtools/gn"

[dehengxu]

I clone dart-sdk from https://github.com/dart-lang/sdk.git to dart-sdk, checkout tag 2.7.2
Run ./tools/build.py --mode release --arch=x64 create_sdk in dart-sdk.
Prompts error:

Running python mypath/dart-sdk/tools/generate_buildfiles.py
Couldn't find the gn binary at path: mypath/dart-sdk/buildtools/gn
Couldn't find the gn binary at path: mypath/dart-sdk/buildtools/gn
Tried to run GN, but it failed. Try running it manually:
    $ python mypath/dart-sdk/tools/gn.py -m debug -a x64 --os host -v

[vsmenon]

Note, you cannot clone the git repo directly and build. You need to follow the instructions here (gclient) here:

https://github.com/dart-lang/sdk/wiki/Building