Thanks for your bug report!
I have spotted the issue and fixed it in VCS. Please see:
libunwind and safe-iop are indeed needed in stage1, as well as pandoc
(I guess you had typos?). We never intended to set a stage for "nodoc"
which, so I also included it in stage1.
However I'm not sure about your point of self dependency of
andoid-platform-system-core-headers. This package does not
build-depend on it, but instead depends on