Revert "out of tree build: ruby"

Revert "out of tree build: ruby"

This reverts commit 48d2e0d9ea5c12ae81f31706fa463f8e1ebd09af.

This commit breaks the ordinary build:

make[2]: Entering directory `/home/rjones/d/hivex/ruby'
rake build
rake/rdoctask is deprecated.  Use rdoc/task instead (in RDoc 2.4.2+)
rake/gempackagetask is deprecated.  Use rubygems/package_task instead
top_srcdir=$(pwd)/..; top_builddir=$(pwd)/..; export ARCHFLAGS="-arch $(uname -m)"; mkdir -p ./ext/guestfs; cd ./hivex; ruby #(EXT_CONF} --with-_hivex-include=$top_srcdir/lib --with-_hivex-lib=$top_builddir/lib/.libs
sh: line 0: cd: ./hivex: No such file or directory