buildworld fail in stable/11 @r325033 -- r325029?

[Harry Schmalzbauer]

 Bezüglich David Wolfskill's Nachricht vom 27.10.2017 13:12 (localtime):
> This is observed on systems (both my laptop & my build machine) running
> stable/11 @r325003, after updating sources to r325033:
>
> --- libprocstat.o ---
> In file included from /usr/src/lib/libprocstat/libprocstat.c:69:
> /usr/obj/usr/src/tmp/usr/include/sys/ptrace.h:148:19: error: field has incomplete type 'struct siginfo32'
>         struct siginfo32 pl_siginfo;    /* siginfo for signal */
>                          ^
> /usr/obj/usr/src/tmp/usr/include/sys/ptrace.h:148:9: note: forward declaration of 'struct siginfo32'
>         struct siginfo32 pl_siginfo;    /* siginfo for signal */
>                ^

I know nothing about the code changes in r324932 (MFC r316286), but the
followup fix r325029 (MFC r320481) seems to have caused the early
buildworld failure in stable/11 – for me too.
Since clang reported the error referencing some include from obj/tmp
(tmp/usr/include/sys/ptrace.h), I found:
r316304
(https://svnweb.freebsd.org/base/head/lib/libprocstat/libprocstat.c?view=patch&r1=316304&r2=316303&pathrev=316304),
which I thought could explain the symptom.
Seems to be the solution (applies cleanly to stable/11, buildworld
succeded). Even a blind squirrel sometimes finds the nut ;-)

-harry