posix_spawn - implement support for POSIX_SPAWN_CLOEXEC_DEFAULT am: 06b249fc75 am: 2456232406

Original change: https://googleplex-android-review.googlesource.com/c/platform/bionic/+/17951150

Change-Id: Ibe9c6400e6cd6c0d0fd40cf14f697e70cc0d5633
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>