Always install built packages.
At this point, install_success_file ('.install') is ignored, as we are always re-installing.
This should be much safer than previous logic, which would try to forego installing. This made lane packaging on wrench unreliable and hard to debug.
Bockbuild now only caches checkouts and builds, but does not "resume" from incomplete (and possibly problematic) packaging material.
Build fontconfig with --with-cache-dir.

This enables fontconfig to correctly fallback to caching to ~/Library/Caches if mono
is not installed. This affects XamMac apps as fontconfig would rebuild its cache every single time.
Build tar with --enable-nls=no, without this, it seems to crash when invoking gzip if LC_CTYPE/LANG are not set.
Revert "Build fontconfig with --with-cache-dir."
The commit breaks the build, as fontconfig's configure scripts don't seem to be able to handle '~' in the '--with-cache-dir' arguments. Alternatively using ${HOME} instead actually works, but a) Bockbuild's own macro expansion rules try to expand ${HOME} and b) cache-dir with ${HOME} seems to be expanded at build-time which I do not think was the idea for this change. Will discuss with @duncanmak and @kumpera.

This reverts commit 0aac9b0881029bff125e11ae4bc7e4c223f828da.
Reintroducing fontconfig caching change, but skipping build-time fc-cache.
Build-time fc-cache fails when using the 'with-cache-dir' argument, which is needed as per reverted commit 0aac9b0881029bff125e11ae4bc7e4c223f828da
This also has the added advantage of speeding up packaging, since the cache is not used and takes over a minute to build.
Update mono config generation

Mono PR mono/mono#1064 changes how the paths for libMonoPosixHelper
and libgdiplus stored in the configuration file are computed. This
means that no fixing is needed anymore for libMonoPosixHelper, because
the intallation prefix is automatically added. Instead libgdiplus is
assumed to be in the default library load path unless another path is
specified at configure-time through the --with-libgdiplus option.
Merge commit '440a451ffa8152cf9e3e4d1634596cd6ecf2218e' into alexischr-mono-mac-64-package
Need '--with-libgdiplus' to make tests work on 64-bit package.