[CMake] ExternalProject, continuous integration and caching builds

[Antoine Pitrou]

Le 05/09/2018 à 14:37, Antoine Pitrou a écrit :
> 
>> When AppVeyor restores the cached directories and files, does it also
>> preserve their timestamps? If not, that might explain why it always
>> rebuilds.
> 
> I do not know.  I've found out this utility:
> https://github.com/iboB/mtime_cache and will experiment with it.

It turns out that doesn't solve the issue.  One likely explanation is
that fixing the timestamps on cached contents is not useful if
ExternalProject unpacks the downloaded tarball again and overwrites the
source files.

One thing is that we build many of those dependencies in-source (using
BUILD_IN_SOURCE), since they don't necessarily support out-of-tree builds...

Regards

Antoine.