Allow to replace ln -fs and hardlink on Windows by default

[oech3]

Allow to replace ln-fs by make LN=ln (Minimized replacement for #8790 and #7928 ).

Reasons:

1. Windows does not allow symlinking by default. It blocks to build this as single binary at MSYS2.
2. AppArmor needs proper argv[0] .

I have no idea what test should we have for this feature.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

[codspeed-hq]

CodSpeed Performance Report

Merging #8810 will not alter performance

_{Comparing oech3:ln (6cdf6aa) with main (be25344)}

Summary

✅ 69 untouched
⏩ 73 skipped¹

Footnotes

1. 73 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[sylvestre]

Please add a github action test. That will do

[oech3]

Added tests for LN=

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)