test suite fails on hppa (0.4.5.5-rc)
Debian#981648: tor FTBFS on hppa was reported, and it came with a patch/pull-request on github.
The affected code is many years old (it was added in 2013).
The issue appears to be that the linux/hppa kernel changed the O_NONBLOCK constant, so you can't just do (flags & FOO) == FOO to check if foo is set, you better do (flags & FOO) != 0. The patch concerns itself with O_NONBLOCK, but it probably also applies to FD_CLOEXEC.