speeding up build on windows - Failed to parse file

Thanks in advance for any help.

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[ ] feature request
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Current behavior
Running the below command as per instructions in speeding up build on windows wiki page
tsc --project tsconfig.json

throws error:
error TS5014: Failed to parse file 'tsconfig.json/tsconfig.json': Unexpected token u in JSON at position 0.

Expected behavior
compile tools to js files

Minimal reproduction of the problem with instructions
tsc --project tsconfig.json

Please tell us about your environment:
OS: Windows 10
IDE: VSCode v1.17.2
NPM v4.0.2
node v 6.9.1

• Angular Seed Version: 234a5fed2bc74ec6dceb32b6ddf09dcc504b4083

• Node: node --version = 6.9.1

Start by reproducing tsc --project tsconfig.json on Windows 10 with the reported Node 6.9.1 and TypeScript setup, then inspect how tsconfig.json is being resolved. Compare the result with the speeding-up-build-on-Windows instructions; done means the tools compile to JavaScript without the TS5014 parsing error.