It is a portable version of the realpath(1) utility that you can find on Mac OS X and FreeBSD (see also The Open Group Base Specifications Issue 6, IEEE Std 1003.1). Without the -P flag, pwd(1) might return different values when the current path contains one or more symlinks, depending on how you got into the current directory. In simplenode.runner, this may cause PIPE_DIR to have different values on each use, which will make it impossible to connect to the running node unless you guess the correct path yourself.
Since R15B02, ct_run returns a non-zero exit code when some tests failed or were auto-skipped. (See ticket OTP-9865.) This fix makes it so a non-0 code doesn't cause an instant failure, but still prompts for log verification before doing so. Given the behaviour was acceptable for pre-R15B02, it should be valid with it with post-R15B02. The fix should also be backwards compatible.
As discussed here http://erlang.org/pipermail/erlang-questions/2012-December/071135.html change the reltool spec to use the default sys-level mod_cond setting.