bug#69770: [PATCH] build: strengthen 16 bit float support checks

[Collin Funk]

On 3/14/24 6:03 AM, Pádraig Brady wrote:
> It would disable this feature for cross-compilation yes,
> but this isn't the first instance of AC_RUN_IFELSE we use.

Sorry if this is not the proper place to ask, but would it be possible
to make Autoconf use an emulator when cross-compiling? This issue
would be *less* of a problem in that case.

I am more familiar with CMake where check_c_source_runs is used
performs a similar task [1]. It is essentially a wrapper function
around try_run [2]. CMake allows you to set
CMAKE_CROSSCOMPILING_EMULATOR which will make try_run use an emulator
to run programs instead [3].

I've used this with Wine and QEMU User a few times and it makes
CMake's configure tests work fine (though much slower). If this
functionality seems beneficial then I can look into adding it to
Autoconf.

[1] https://cmake.org/cmake/help/latest/module/CheckCSourceRuns.html
[2] 
https://github.com/Kitware/CMake/blob/4285dec5f012260337193f29f18899d6cf2536a4/Modules/Internal/CheckSourceRuns.cmake#L93
[3] 
https://cmake.org/cmake/help/latest/variable/CMAKE_CROSSCOMPILING_EMULATOR.html

Collin