[3.13] libpython: drop the unused C++ compiler

[MilesCranmerBot]

Why

Backport of #950 (3.14) and #949 (main), for #951. libpython on this branch depends on libstdcxx >=15 through the C++ compiler's run-export, but the library links no C++ runtime: objdump -p on libpython3.13.so.1.0 from the current linux-64 build lists only libc, libm, libpthread, libdl, libutil (and ld-linux). Because python pins libpython exactly, environments that cap libstdc++ below 15 (Julia 1.10 and 1.12 via CondaPkg) cannot install current python 3.13 builds.

Scope

The same two commits as #950: drop {{ compiler('cxx') }} from the libpython output's build requirements, create $PREFIX/lib before copying the library (on macOS that directory was only created by the compiler's libcxx run-export), and bump the build number.

Verification

#950 is the same change and passed CI on all platforms; the fixed 3.14.8 build (hd51c5da_102_cp314) is published without libstdcxx.

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe/meta.yaml) and found it was in an excellent condition.

I do have some suggestions for making it better though...

For recipe/meta.yaml:

• ℹ️ The recipe is not parsable by parser conda-souschef (grayskull). This parser is not currently used by conda-forge, but may be in the future. We are collecting information to see which recipes are compatible with grayskull.
• ℹ️ The recipe is not parsable by parser conda-recipe-manager. The recipe can only be automatically migrated to the new v1 format if it is parseable by conda-recipe-manager.

_{This message was generated by GitHub Actions workflow run https://github.com/conda-forge/conda-forge-webservices/actions/runs/38421393614. Examine the logs at this URL for more detail.}

[conda-forge-admin]

Hi! This is the friendly conda-forge automerge bot!

I considered the following status checks when analyzing this PR:

• linter: passed
• azure: passed
• github-actions: passed

Thus the PR was passing and merged! Have a great day!