[NinjaBuildCommand] Drop numBuiltInputs, which wasn't used for anything.
[NinjaBuildCommand] Drop numBuiltInputs, which wasn't used for anything.

apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild