For reasons that are a bit beyond me, `--host` and `PLATFORM_TRIPLET`
seem to be independent, in particular we've had an empty
`PLATFORM_TRIPLET`. This is unfortunate because `PLATFORM_TRIPLET`
is used to generate the SOABI config variable which in turn is used
to decide whether a .so file is a good match for loading. We'd like
for linux Pythons not to try to import emscripten .so files (it
raises `ImportError: some_file.so: invalid ELF header`). Similarly,
we'd like to avoid attempting to load linux .so files in wasm. These
platform tags are our friends.

Anyways, this PR sets `PLATFORM_TRIPLET` and ensures that .so files
built by pywasmcross are tagged with our SOABI tag.

I moved the .so file renaming from pywasmcross to buildpkg just
before running the post script. That is a better place to put it in
case the package wants to look at the .so file after linking it. It
might be surprised that we moved it.

I also improved the error message if we try to `loadWebAssemblyModule`
something that is actually say a Linux .so file and updated get_dynlibs
to filter out .so files that have an incompatible abi tag.
Set PLATFORM_TRIPLET, include platform in so names, only load compatible so files. For reasons that are a bit beyond me, `--host` and `PLATFORM_TRIPLET`
seem to be independent, in particular we've had an empty
`PLATFORM_TRIPLET`. This is unfortunate because `PLATFORM_TRIPLET`
is used to generate the SOABI config variable which in turn is used
to decide whether a .so file is a good match for loading. We'd like
for linux Pythons not to try to import emscripten .so files (it
raises `ImportError: some_file.so: invalid ELF header`). Similarly,
we'd like to avoid attempting to load linux .so files in wasm. These
platform tags are our friends.

Anyways, this PR sets `PLATFORM_TRIPLET` and ensures that .so files
built by pywasmcross are tagged with our SOABI tag.

I moved the .so file renaming from pywasmcross to buildpkg just
before running the post script. That is a better place to put it in
case the package wants to look at the .so file after linking it. It
might be surprised that we moved it.

I also improved the error message if we try to `loadWebAssemblyModule`
something that is actually say a Linux .so file and updated get_dynlibs
to filter out .so files that have an incompatible abi tag.
package:
  name: pyerfa
  version: 2.0.0.1
source:
  url: https://files.pythonhosted.org/packages/78/fd/0148f0e54f0c6f48a141409df65d74a5f1dae2e139f23d50a43c58c16098/pyerfa-2.0.0.1.tar.gz
  sha256: 2fd4637ffe2c1e6ede7482c13f583ba7c73119d78bef90175448ce506a0ede30
requirements:
  run:
    - numpy
test:
  imports:
    - erfa
about:
  home: https://github.com/liberfa/pyerfa
  PyPI: https://pypi.org/project/pyerfa
  summary: Python bindings for ERFA
  license: BSD 3-Clause License

package:
  name: pyerfa
  version: 2.0.0.1
source:
  url: https://files.pythonhosted.org/packages/78/fd/0148f0e54f0c6f48a141409df65d74a5f1dae2e139f23d50a43c58c16098/pyerfa-2.0.0.1.tar.gz
  sha256: 2fd4637ffe2c1e6ede7482c13f583ba7c73119d78bef90175448ce506a0ede30
requirements:
  run:
    - numpy
test:
  imports:
    - erfa
about:
  home: https://github.com/liberfa/pyerfa
  PyPI: https://pypi.org/project/pyerfa
  summary: Python bindings for ERFA
  license: BSD 3-Clause License
