posix_spawn - implement support for POSIX_SPAWN_CLOEXEC_DEFAULT am: 06b249fc75

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

Change-Id: I6b687d4ea200b21fa3c82a7dfdcfe905776e76ad
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>