Portindex: can't read "bazel.build_opts": sysctl not available (when faking platform on linux)

[arjunsalyan (Arjun Salyan)]

I am generating the PortIndex on linux using the following command

portindex -p macosx_19_i386

But for certain ports, I am getting issues related to sysctl

Warning: Failed to open old entry for python/py-tensorflow, making a new one
Adding port python/py-tensorflow
Failed to parse file python/py-tensorflow/Portfile with subport 'py37-tensorflow': can't read "bazel.build_opts": sysctl not available
Failed to parse file python/py-tensorflow/Portfile with subport 'py38-tensorflow': can't read "bazel.build_opts": sysctl not available
Failed to parse file python/py-tensorflow/Portfile with subport 'py39-tensorflow': can't read "bazel.build_opts": sysctl not available

Another type of errors encountered are:

Failed to parse file math/pari/Portfile: sysctl not available

I am running MacPorts using a Docker container on Ubuntu 20.0.4. The build was done using latest source code from [macports-base](​https://github.com/macports/macports-base/tree/85d5e10e1fbfc30ad7f7214f2d0b277023213820) repo.