Force precompile_workloads to always be a compile-time preference

[staticfloat]

In order for a preference to be considered a compile-time preference (and therefore for it to invalidate a precompilation cache file) the preference must be read during compilation of a module. The precompile_workloads preference was not being read during PrecompileTools' compilation, but during compilation of modules using PrecompileTools (which is harmless, but does not mark the preference as compile-time for PrecompileTools, of course).

This adds a dummy read of the preference in order to mark it as compile-time, so that adding a precompile_workloads = false in your LocalPreferences.toml properly invalidates everything.

[staticfloat]

This closes #62

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.47%. Comparing base (990c356) to head (5603ade).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #63   +/-   ##
=======================================
  Coverage   82.47%   82.47%           
=======================================
  Files           3        3           
  Lines          97       97           
=======================================
  Hits           80       80           
  Misses         17       17           

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[vchuravy]

I am not a fan of precompile_workloads to begin with, it forces an extremely wide invalidation of the cache.

When I discussed this with @timholy back in the day, my goal with encouraging the use preferences was that invalidation would be as local as possible.

I agree that this the "right" change for #62, but the load in workload_enabled should probably then use the result of this, to tie them together explicitly.

The bigger question is, does this work reliably?

[Plots]
precompile_workload = false

[staticfloat]

That did work in my testing, I figured that @KristofferC had a good reason for wanting to invalidate the world.

[timholy]

Ah, I had missed that it was specifically PrecompileTools' own setting that was at issue.

I agree that the point of that setting is the one in #63 (review). However, if we disable its own precompilation locally, and other packages are devved to use that version, then I guess technically we really should recompile the whole stack, no?