First pass for
#841.

There's some `3.9` still left in
https://github.com/hugovk/python-build-standalone/blob/main/cpython-unix/targets.yml
because seven targets _only_ support 3.9, like `aarch64-apple-ios` and
`arm64-apple-tvos`:


https://github.com/hugovk/python-build-standalone/blob/2181bddcc918f14275232ad6d1365035f2ae75c4/cpython-unix/targets.yml#L114-L119

Should they be removed? Or upgraded?

Also ran `ruff check --select UP --target-version py310 --fix` and `run
check --fix`. There's a lot of `--unsafe-fixes` that can be applied, but
they can be in their own PR to avoid making this too big.

Use `-O0` when building all projects for the debug option and `-O3` in
other cases. Individual build script can adjust these if needed.

closes #849 
partially addresses #846

In version 5.6.0 and newer, liblzma is licensed under the BSD Zero Clause License (0BSD).

Closes #855 

Please see the above issue description for why this addition is proposed

Update the cpython-3.15 target from 3.15.0a1 -> 3.15.0a2