ChildPortHandshake: 10.6 fix.
ChildPortHandshake: 10.6 fix.

The F_SETNOSIGPIPE fcntl() command is not available on 10.6. Use
socketpair() instead of pipe(), so that the SO_NOSIGPIPE socket option
can be used.

TEST=util_test ChildPortHandshake.*
R=rsesek@chromium.org

Review URL: https://codereview.chromium.org/777573002

chromium/crashpad,Chilledheart/crashpad,hokein/crashpad,hankbao/Crashpad,Chilledheart/crashpad,atom/crashpad,Chilledheart/crashpad,hokein/crashpad,hankbao/Crashpad,hankbao/Crashpad,hokein/crashpad,chromium/crashpad,atom/crashpad,chromium/crashpad,atom/crashpad