dev-util/android-ndk-8b is latest version in Portage. Version 8c was released this November.
Created attachment 332848 [details]
I haven't tested it yet but I'm attaching just slightly altered 8b ebuild.
8d was released in December.
8e was released in march
*android-ndk-8d (27 Dec 2012)
*android-ndk-8c (27 Dec 2012)
27 Dec 2012; Joshua Kinard <email@example.com> +android-ndk-8c.ebuild,
Add NDK r8c and r8d, and support gcc-4.7 in r8d. No clang yet.