configure: Set PKG_CONFIG_PATH to get the right settings for the target host.

[Sebastian Lackner]

On 06.06.2017 17:52, Francois Gouget wrote:
> On Tue, 6 Jun 2017, Michael Müller wrote:
> 
>> Setting PKG_CONFIG_PATH doesn't seem like a good option for me. You
>> would need to implement the path for every possible distribution and
>> platform to not cause any regressions.
> 
> You may be thinking of PKG_CONFIG_LIBDIR which overrides the 
> system defaults. PKG_CONFIG_PATH only prepends to the system defaults so 
> that if the .pc files are not found there they are still looked up in 
> all the standard places.
> 
> 
>> On Arch Linux it is for example /usr/lib32/pkgconfig. On FreeBSD it is 
>> /usr/libdata/pkgconfig/.
> 
> Maybe a few more paths will need to be added but their absence will not 
> make things worse.
> 
> 
>> Not to speak of cross compilation cases in which users might have a 
>> special build of pkgconfig where overriding PKG_CONFIG_PATH doesn't 
>> make any sense.
> 
> That's why PKG_CONFIG_PATH is only set if $cross_compiling is false in 
> the 32 bit case. The 64 bit case does not seem to have any qualms 
> forcing CC="$CC -m64" regardless of $cross_compiling so I'm aligning 
> myself with that until I know why it should be different.
> 

The 32-bit case shouldn't cause any problems and looks fine to me, but
the 64-bit case would break our cross compilation for macOS. Adding
"-m64" doesn't matter, however setting PKG_CONFIG_PATH means that host
pkgconfig information is used instead of the correct one. Of course it
can be worked around with a cross compilation check, but I'm wondering
if it wouldn't be better to omit this hack for 64-bit and only focus
on the 32-bit case.

Best regards,
Sebastian