Fix autotools install on Windows

[SpaceIm]

Changelog: Bugfix: Fix Autotools install on Windows. The default argument passed is DESTDIR=unix_path(self, self.package_folder).
Docs: conan-io/docs#2801
Closes #12153

• Refer to the issue that supports this Pull Request.
• If the issue has missing info, explain the purpose/use case/pain/need that covers this Pull Request.
• I've read the Contributing guide.
• I've followed the PEP8 style guides for Python code.
• I've opened another PR in the Conan docs repo to the develop branch, documenting this one.

^{Note: By default this PR will skip the slower tests and will use a limited set of python versions. Check here how to increase the testing level by writing some tags in the current PR body text.}

[memsharded]

It is looking good, but we would need a test that fails without this fix.
There are subsystems like msys2 installed in our CI, it should be possible, look for pytest.mark.tool_msys2 or something like that, or ask for help if you need it, and we can try to contribute a test

[SpaceIm]

Yes. I guess https://github.com/conan-io/conan/blob/4cfd5af2f6e1ead79ce173aebf61b50dbe440a81/conans/test/functional/toolchains/gnu/autotools/test_win_bash.py could be a good source of inspiration. Actually it could be extended since it already test AutotoolsToolchain & Autotools build on Windows, but without going until installation.

[SpaceIm]

Need some help here, I can't reproduce this issue on Windows in the test when I remove the fix.