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.
Disable ligatures in Pango. Using the CoreText backend we can't visually move the caret
position inside ligatures, so the caret position gets offset when you try to key around
inside a GtkEntry that contains any ligatures, e.g. "fluid" has "fl" ligature so the
caret is offset by 1.

https://bugzilla.xamarin.com/show_bug.cgi?id=15787
Merge pull request #7 from ranma42/fix-config-paths

Update mono config generation to match config path fixes in mono/mono#1064