make precompile files writable

[KristofferC]

The combination of #34573 and JuliaLang/Pkg.jl#785 means that the precompile files are currently not writable. This means that our way of updating the use time of precompile filkes in

julia/base/loading.jl

Line 835 in 2893de7

touch(path_to_try) # update timestamp of precompilation file

which is then used for sorting:

julia/base/loading.jl

Lines 739 to 742 in 2893de7

	# allocating the sort vector is less expensive than using sort!(.. by=mtime), which would
	# call the relatively slow mtime multiple times per path
	p = sortperm(mtime.(paths), rev = true)
	return paths[p]

is no longer functional.

Fix this by making sure the precompile file is writable.

[codecov]

Codecov Report

Merging #41614 (2893de7) into master (2893de7) will not change coverage.
The diff coverage is n/a.

❗ Current head 2893de7 differs from pull request most recent head 7df3587. Consider uploading reports for the commit 7df3587 to get more accurate results

@@           Coverage Diff           @@
##           master   #41614   +/-   ##
=======================================
  Coverage   81.84%   81.84%           
=======================================
  Files         350      350           
  Lines       73941    73941           
=======================================
  Hits        60520    60520           
  Misses      13421    13421           

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[IanButterworth]

Perhaps this could explain why some people see packages being precompiled again unexpectedly, if the sort was only respecting creation time, not last used time, and the wrong caches were being tidied up.

Also, this might speed things up a bit, with the sort doing the thing it was intended to do.