glib2: make environment name customizable
glib2: make environment name customizable

It is useful for not PATH environment variable such as GI_TYPELIB_PATH
that is GObjectIntrospection's .typelib search path.

kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2