Debug: Remove Excess System Calls

[dthain]

Proposed Changes

On Linux, every single debug() event was resulting in the following system calls:

stat("/etc/localtime")
getpid()
getpid()
getpid()
write(fd,event)

With the sort of extensive debugging output emitted by taskvine, the cost of debug messages was becoming surprisingly high. This PR reduces the cost to:

getpid()
write(fd,event)

Note that getpid() was previously cached and the system call optimized away, but this is no longer true:
https://sourceware.org/glibc/wiki/Release/2.25#pid_cache_removal

It turns out that it is surprisingly hard to catch all variations of fork() in order to invalidate such a cached value.

Maybe we don't need to write it to every debug line?

Merge Checklist

The following items must be completed before PRs can be merged.
Check these off to verify you have completed all steps.

• make test Run local tests prior to pushing.
• make format Format source code to comply with lint policies. Note that some lint errors can only be resolved manually (e.g., Python)
• make lint Run lint on source code prior to pushing.
• Manual Update: Update the manual to reflect user-visible changes.
• Type Labels: Select a github label for the type: bugfix, enhancement, etc.
• Product Labels: Select a github label for the product: TaskVine, Makeflow, etc.
• PR RTM: Mark your PR as ready to merge.

[dthain]

Merge when you are ready...