ruby: Split tarball location/checksum from common cmmi options and environment

In the next patch we'll add another version of Ruby, and it will make
sense to share common configuration for Ruby compiling.

/cc @kazuhiko

component/ruby/buildout.cfg

@@ -12,10 +12,8 @@ extends =
 
 parts = ruby
 
-[ruby2.2]
+[ruby-common]
 recipe = slapos.recipe.cmmi
-url = http://ftp.ruby-lang.org/pub/ruby/2.2/ruby-2.2.2.tar.xz
-md5sum = dbce9b9d79d90f213ba8d448b0b6ed86
 configure-options =
   --enable-shared --enable-rpath --disable-install-doc
   --with-out-ext=tk,tk/tkutil,win32,win32ole
@@ -25,5 +23,12 @@ environment =
   LDFLAGS=-L${gdbm:location}/lib -L${libffi:location}/lib -L${libyaml:location}/lib -L${ncurses:location}/lib -L${openssl:location}/lib -L${readline:location}/lib -L${zlib:location}/lib -Wl,-rpath=${gdbm:location}/lib  -Wl,-rpath=${libffi:location}/lib -Wl,-rpath=${libyaml:location}/lib -Wl,-rpath=${ncurses:location}/lib -Wl,-rpath=${openssl:location}/lib -Wl,-rpath=${readline:location}/lib -Wl,-rpath=${zlib:location}/lib
   PKG_CONFIG_PATH=${libyaml:location}/lib/
 
+
+[ruby2.2]
+<= ruby-common
+url = http://ftp.ruby-lang.org/pub/ruby/2.2/ruby-2.2.2.tar.xz
+md5sum = dbce9b9d79d90f213ba8d448b0b6ed86
+
+
 [ruby]
 <= ruby2.2