This change complements #4749. Installing the Ruby mapscript library in /usr/lib/ruby// is wrong, while Debian packages installed modules there this is not correct for MapServer upstream.
The installation directory is changed to /usr/local/lib/ruby/site_ruby//, quite similar to the Perl mapscript installation directory /usr/local/lib/perl/5.14.2.
The Debian packages modify CMakeLists.txt to use vendorarch instead to install in the /usr prefix instead of /usr/local.
Install Ruby mapscript in sitearchdir instead of archdir.
@sebastic or @tbonfort, should this also be applied to branch-6-4?
crap, I let this one through... cherry-picked for 6.4.1 in a70d192
Install Ruby mapscript in sitearchdir instead of archdir (#4754)