This is so called "seems to work in dry tests" commit which is aimed to switch
linux release environment to CMake.
Some notes:
- There's no special handle of libstdc++, but it wasn't really static for quite
some time in SCons configuration and nobody really complained.
- It was quite tricky to get OpenMP linked statically with just using some
configuration so we went ahead and added a special option to CMake now which is
only exist on Linux and advertised as shouldn't be used.
- Packing is happening manually in slave_pack.py. This is because we have to add
some really special files to the archive (mesa libraries for example) which we
can't really handle from CMake/CPack in a nice generic way.
Don't think it's bad approach, at least crappynness is localized and it's not
_that_ crappy anyway.
- Windows buildbot should keep working, but needs doublechecing. It's just a
build folder changed, but you never know what it might imply.
- Some further tweaks are likely needed to ensure all builders are working.
Thanks Campbell for assistance in this patch!
