NH-35046 No longer need PLATFORM env var for sdist installation, tests

[tammy-baylis-swi]

Fixes an issue where PLATFORM environment variable is required by customers(!) to install Python APM library from sdist, i.e. on Alpine Linux. Thank you @cheempz for spotting this.

PLATFORM is no longer mandatory for extension creation by setuptools (setup.py) nor testing. I published this as TestPyPI version 0.8.1.4 and I tested installation of this with:

1. Change this line in testbed to RUN pip install --extra-index-url https://test.pypi.org/simple/ --no-binary solarwinds-apm solarwinds-apm==0.8.1.4 to force installation from sdist instead of wheels.
2. Build test app without setting ENV for platform: docker-compose -f docker-compose.flask-from-testpypi.yml build --no-cache
3. No longer gets pip error at build

Install tests pass after removing PLATFORM from verify_install.yaml: https://github.com/solarwindscloud/solarwinds-apm-python/actions/runs/4359203186

I can run the testbed without PLATFORM now; changes in this PR.

PLATFORM is optional for some make actions (Makefile): built wheel tagging (in GH workflows for releases or local make package) and lambda builds. If not provided, PLATFORM defaults to x86_64. PLATFORM=aarch64 is provided by the build_publish_aarch64 GH actions that build aarch64 on QEMU (where uname -m doesn't seem to be aarch64).

This also makes the --no-binary / --only-binary pip calls in the install tests less ambiguous/more correct.

[cheempz]

LGTM pending minor question, thanks for addressing this so quickly @tammy-baylis-swi!

[cheempz]

Minor is the addition of solarwinds-apm needed? Seeing later that we do seem to append it to pip_options.

[tammy-baylis-swi]

I think it is, technically. pip --only-binary and --no-binary are supposed to have a <format_control> value provided: https://pip.pypa.io/en/stable/cli/pip_install/#cmdoption-only-binary

The way it's currently written in the install tests still works and I'm not sure why given the above. The install tests pass on GH (have been for a long time) and this also passes on my local on main branch: MODE=testpypi docker-compose run --rm py3.7-install-alpine3.12.

The missing <format_control> becomes an issue when I try to install from the testbed for flask-from-testpypi. Both of these error:

pip install --no-binary solarwinds-apm==0.8.0
pip install --no-binary solarwinds-apm

But this is ok:

pip install --no-binary solarwinds-apm==0.8.0 solarwinds-apm

Actually this is failing too...

pip install --no-binary solarwinds-apm solarwinds-apm

...Ok. I'm going to revert b7fcfd6 and do a fresh publish and test.

[tammy-baylis-swi]

Thanks for first review @cheempz ! I've reverted b7fcfd6, published to TestPyPI as 0.8.1.5, and run the install tests again which seem ok: https://github.com/solarwindscloud/solarwinds-apm-python/actions/runs/4369183330

Please could you have another look and let me know if anything else needed 😃

[cheempz]

LGTM, thanks for the revisit @tammy-baylis-swi!