gentoo-overlay/dev-lang/ruby/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
  <herd>ruby</herd>
  <use>
    <flag name="rubytests">
      Install ruby tests that can only be run after ruby is installed
    </flag>
    <flag name="readline">
      Use the <pkg>sys-libs/readline</pkg> library to provide the
      readline extension, used for instance by the irb tool. This flag
      is meaningful only if the libedit USE flag is disabled.

      If neither libedit nor readline USE flags are enabled, the
      readline extension will not be built (and irb will lose line
      editing functionality).
    </flag>
    <flag name="rdoc">
      Install <pkg>dev-ruby/rdoc</pkg> after installing Ruby.
    </flag>
    <flag name="jemalloc">
	  Use <pkg>dev-libs/jemalloc</pkg> for memory allocation.
	</flag>
  </use>
</pkgmetadata>