synopsis: Use process jobs when spawning subprocesses
prs: #6529 #6536

description: {

Many toolchain tools written for POSIX systems rely on the exec system
call. Unfortunately, it is not possible to implement exec in a
POSIX-compliant manner on Windows. In particular, the semantics of the
exec implementation provided by the widely-used msvcrt C runtime
will cause process's waiting on the exec'ing process to incorrectly
conclude that the process has successfully terminated when in fact it is
still running in another process.

For this reason, the process library exposes the use_process_jobs
flag to use a more strict (although still not POSIX-compliant) mechanism
for tracking process completion.
This is explained in [the Process.hs comment](https://github.com/haskell/process/blob/master/System/Process.hs#L399)

Unfortunately, job support in the process library is currently quite
broken and was only recently fixed. Consequently, we only enable job
object support for process releases >= 1.6.8.

}