MFC r300662

Fix Coverity CID 1016714 Resource leak in process_file_actions_entry()

Don't leak a file descriptor of _dup2() fails (shouldn't happen).

Reported by: Coverity
CID: 1016714

MFC r287292:
Switch libc from using _sig{procmask,action,suspend} symbols, which
are aliases for the syscall stubs and are plt-interposed, to the
libc-private aliases of internally interposed sigprocmask() etc.

MFC r287300:
Use libthr interposed functions instead of syscalls, in posix_spawn()'
child.

MFC r287292:
Switch libc from using _sig{procmask,action,suspend} symbols, which
are aliases for the syscall stubs and are plt-interposed, to the
libc-private aliases of internally interposed sigprocmask() etc.

MFC r287300:
Use libthr interposed functions instead of syscalls, in posix_spawn()'
child.