python@3.10: skip LTO on Linux

[carlocab]

Fixes Homebrew/discussions#3734.

This is essentially the same issue as #112154, except that I'm not aware
of a way to convert the bitcode for GCC. It's possible that there is no
way to do this, given that GCC seems to consider its IR as an internal
implementation detail.

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[carlocab]

This should probably be backported to the other python@3.* formulae.

[cho-m]

Does this fix the vim issue (which is the main issue in the discussion rather than source-build)? We pretty much always hit vim failure in Homebrew Linux CI for every Python bump because the binary is burning in the Cellar paths.

• 3.10.4 -- python@3.10 3.10.4 #97010 (comment)
• 3.10.5 -- python-tk@3.10 python@3.10 3.10.5 #103101 (comment)
• 3.10.6 -- python{,-tk}@3.10 3.10.6 #107164 (comment)

[carlocab]

It may. I'm not sure. One thing worth checking is the output of strings libpython3.10.a before and after this change.

My guess is that this does not fix it. Even Python.framework on macOS embeds a Cellar reference, so this path is likely referred explicitly in the source somewhere.

The proper fix for that would likely be to make sure Vim links with libpython3.so instead. Embedding the interpreter statically isn't that useful because you still need all the extra stuff that comes with Python (e.g. the bundled Python libraries). It's really not clear why you would link statically when you still need that.

[BrewTestBot]

🤖 A scheduled task has triggered a merge.

[carlocab]

I think we need to set

--enable-python3interp=dynamic

to make sure we link with the shared library on Linux when building Vim.

There is a libpython3.a on macOS, but that's just a symlink to the Python framework so you'll get shared linkage anyway.