GentooPrefix on MacOSXでghcがビルドできない

emerge ghc

したところ、以下のようなエラーでビルドに失敗してしまう。あとで追ってみよう。

...
/* ERROR: dev-lang/ghc-6.8.2-r1 failed:
 *   Could not locate bundled libreadline.so
 * 
 * Call stack:
 *     ebuild.sh, line  51:  Called call-ebuildshell 'src_compile'
 *   environment, line 915:  Called src_compile
 *   environment, line 4017:  Called die
 * The specific snippet of code:
 *           die "Could not locate bundled libreadline.so";
 *
...