Errored: OpenSmalltalk/opensmalltalk-vm#2093 (Cog - 69a6ef7)

Allow build failure of pharo.cog.spur flavor

Hi all, for some time and some unknown reason, pharo builds started to fail while building libssh2-1.7.0 on unix OSes
There is considerable time and resources wasted building always the same libraries, and fragile cache strategies deployed to workaround the problem.
To my knowledge, these failures are completely un-related to VMMaker changes, and probably not to platforms changes either.
It might be related to cache handling (rather the success might be due to the cache preserving previous success...).

The pharo fork changed their strategy and now download pre-build binaries rather than rebuilding them, which is a very wise decision.
So, pharo folks, if you are interested in pharo builds from the root opensmalltalk-vm, please help debug current build and backport those vital changes.
If no one speaks up, we consider those builds as non essential.
Thanks for eventual support.