Provide fontconfig configuration which forces antialiasing

In older releases (up to the version present in trusty), fontconfig-config provided
a config file which forced antialiasing. This is no longer present in the versions
in jessie and later, so provide it manually since otherwise some fonts look distorted
in smaller resolutions.

Bug: T139543
Change-Id: I848dd6b068ade935b60f87a2f0d5c844034a759e