Latest main tries to link f(un)lockfile even with FMT_OS OFF

[glebm]

I've tried updating libfmt to the latest git (diasurgical/devilutionX#7457) and it appears the current version attempts to link f(un)lockfile even with set(FMT_OS OFF).

https://github.com/diasurgical/devilutionX/actions/runs/11191322109/job/31114078447?pr=7457

 /opt/devkitpro/devkitARM/bin/../lib/gcc/arm-none-eabi/14.2.0/../../../../arm-none-eabi/bin/ld: /tmp/ccd8bZAp.ltrans51.ltrans.o: in function `fmt::v11::vprint(__sFILE*, fmt::v11::basic_string_view<char>, fmt::v11::basic_format_args<fmt::v11::context>) [clone .constprop.0]':
/__w/devilutionX/devilutionX/build/_deps/libfmt-src/include/fmt/format-inl.h:1679:(.text._ZN3fmt3v116vprintEP7__sFILENS0_17basic_string_viewIcEENS0_17basic_format_argsINS0_7contextEEE.constprop.0+0x30): undefined reference to `flockfile'
/opt/devkitpro/devkitARM/bin/../lib/gcc/arm-none-eabi/14.2.0/../../../../arm-none-eabi/bin/ld: /__w/devilutionX/devilutionX/build/_deps/libfmt-src/include/fmt/format-inl.h:1688:(.text._ZN3fmt3v116vprintEP7__sFILENS0_17basic_string_viewIcEENS0_17basic_format_argsINS0_7contextEEE.constprop.0+0xc4): undefined reference to `funlockfile'
/opt/devkitpro/devkitARM/bin/../lib/gcc/arm-none-eabi/14.2.0/../../../../arm-none-eabi/bin/ld: /tmp/ccd8bZAp.ltrans51.ltrans.o:/__w/devilutionX/devilutionX/build/_deps/libfmt-src/include/fmt/format-inl.h:1688:(.text._ZN3fmt3v116vprintEP7__sFILENS0_17basic_string_viewIcEENS0_17basic_format_argsINS0_7contextEEE.constprop.0+0xe4): undefined reference to `funlockfile'

[glebm]

Looks like there was a similar issue previously (#4054) that got fixed and has now regressed.

Perhaps the detection mechanism broke.

[glebm]

It is also possible that something broke in the open-sources SDKs but it is a bit unusual that it would change in 3 of them:

Version 92227c7 still builds and links OK

[glebm]

Bisecting..

[glebm]

439b6d7 is the first bad commit

commit 439b6d7212d588bc4be890c17f50d4cbf19233a6
Author: Victor Zverovich <[email protected]>
Date:   Sun Jul 21 08:05:07 2024 -0700

    Reenable print optimization

 include/fmt/format-inl.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

[glebm]

Looks like these platforms declare but do not define f(un)lockfile, which is incorrect.

Worked around with:

if(NINTENDO_3DS OR NINTENDO_SWITCH OR VITA)
  target_compile_definitions(fmt PUBLIC FMT_USE_FALLBACK_FILE=1)
endif()