ensure XDG_CACHE_HOME exists

[dl6tom]

while packaging Horizon EDA for OpenBSD i noticed, that when launched from a freshly created user account it fails with

libc++abi: terminating due to uncaught exception of type horizon::SQLite::Error: unable to open database file
Abort trap (core dumped)

that happens cause XDG_CACHE_HOME (~/.cache in this case) does not exist in the home directory yet.

this change ensures it exists and also temporarily changes umask to ensure permissions according to XDG Base Directory Specification.