man_make_section_directory should not be enabled by default

[foutrelis]

Enabling man_make_section_directory by default in #8284 breaks projects relying on the previous behavior. This is a serious problem for Linux distributions that will end up with misplaced and unusable man pages. Please consider keeping it disabled by default; the benefit of being able to use MANPATH in the output directory does not justify this kind of breakage.

I also noticed that the current implementation generates paths like <builddir>/1 instead of <builddir>/man1. Only the latter can be used with MANPATH which appears to be the main motivation behind #7996.

Examples of breakage I've seen so far (and we've only had sphinx 4.0.x in Arch Linux for three days):

fish-shell does not expect the section subdirectory and results in man pages for built-in shell commands being installed to usr/share/fish/man/man1/1 instead of usr/share/fish/man/man1 and also fails to filter out fish.1, fish_indent.1 and fish_key_reader.1 which are meant to be installed to usr/share/man/man1.

llvm-project copies the output directory to usr/share/man/man1 resulting in paths like usr/share/man/man1/1/foo.1 (note the additional 1 directory).

[tk0miya]

Thank you for letting us know. I just reverted the change of default setting in #9232. It will be released as 4.0.2 soon. And I'll change the directory name in #9231. It will be released as 4.1.0.