freebsd: fix bootstrapping tools under Linux/musl

[valpackett]

Motivation and Context

musl libc has deprecated LFS64 aliases, so bootstrapping FreeBSD tools under musl distros has been failing with stat64 errors.

Description

Apply the aliases under non-glibc Linux to fix this problem.

How Has This Been Tested?

This is part of my work on making FreeBSD build under Chimera Linux; it builds :)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[behlendorf]

This is part of my work on making FreeBSD build under Chimera Linux; it builds :)

That's pretty cool.

Can you just address the make cstyle issue, then force update the PR.

[ryao]

This should cause build failures on older versions of musl due to -Werror (unless we are not using it on FreeBSD and I have yet to realize). We should use #ifundef as a guard against multiple definitions to avoid problems on them.

This also would likely cause build failures on systems using uclibc and klibc. At a glance, uclibc appears to mimic glibc while klibc is like musl, but defines these. I am not sure if anyone is using these libcs (or if we even build on them at present), but we probably should also include !defined(__UCLIBC__) in the linux check. klibc should not need an explicit check as long as it has the multiple definition protection meant for older musl libc versions.

[ryao]

@behlendorf Boostrapping FreeBSD on other Linux libcs is likely broken in other places (since I doubt anyone ever does it), so it would not be terrible if you merge this without minor corrections for the portability issues that I raised.

[behlendorf]

@ryao I fully expect there are other compatibility issues out there lurking. We'll have to fix those as they're encountered.