Do a better job with scopers for fds and posix_spawn_file_actions_t.
There's also no need to make a copy of handshaker_path with strdup.
The non-const parameter are because posix_spawn inherits execve's
C problem: unlike C++, C cannot cast from char *const * to
const char *const *, so POSIX APIs are not const-correct.
Finally, we freely use std::vector and friends in tests, so we don't
actually need to depend on bssl::Array.
Change-Id: I739dcb6b1a2d415d47ff9b2399eebec987aab0bc
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/46524
Reviewed-by: Adam Langley <agl@google.com>
David Benjamin
Adam Langley