autoconf: Do not clear "os" from package info

[cubanpit]

Avoids compatibility issues between Windows and Linux.

Summary

Changes to recipe: autoconf

Motivation

Not including os information in the package means that packages built on Linux and Windows mix up, with same package ID and different package revisions. The most recent one will then be pulled from the remote and used, but they might actually not be fully compatible between OSes. In our case the Windows-built version did not have the executable flag set on the scripts in bin/, this caused issues when using the package in a Linux environment.
The symptoms were similar to conan-io/conan#14345, so we initially thought the problem happened in decompressing the package files.

Details

Just keep the os information, it causes minimal duplication and it makes sure the package works in all environments.

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• Read the contributing guidelines
• Checked that this PR is not a duplicate: list of PRs by recipe
• Tested locally with at least one configuration using a recent version of Conan

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All committers have signed the CLA.

[conan-center-bot]

Conan v1 pipeline ✔️

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All green in build 1 (f2ad7f894cde60c13e7bddcb8918d72296a6b8f2):

• autoconf/2.72:
  Built 5 packages out of 11 (All logs)

• autoconf/2.71:
  Built 5 packages out of 11 (All logs)

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All green in build 1 (f2ad7f894cde60c13e7bddcb8918d72296a6b8f2):

• autoconf/2.71:
  Built 4 packages out of 5 (All logs)

• autoconf/2.72:
  Built 4 packages out of 5 (All logs)

[uilianries]

Good catch!

[memsharded]

The self.info.clear() also clears:

• Possible variability from options, not an issue in this case
• Possible variability from dependencies. In this case, it could be a problem as self.requires("m4/1.4.19") is a requirement, and changing that version will create another package_id. Most like the self.info.requires.clear() is necessary too

[cubanpit]

I understand and I added this change to the branch.
I would imagine that a new version of m4 can change the output, but then the package revision would change as well.
A change in the version of m4 would also mean a change in the recipe revision though, so a new package would be generated anyway, does this actually avoid duplication?