S10-packages/precompilation.t should not overwrite existing files

[ugexe]

There are multiple spots in S10-packages/precompilation.t that overwrite modules in packages/. For example:

roast/S10-packages/precompilation.t

Lines 190 to 191 in 99b194b

	my $trigger-file = $rt128156-lib-prefix.IO.add('RT128156/Two.rakumod');
	$trigger-file.IO.spurt($trigger-file.slurp);

These test should instead copy the root distribution path being used, e.g. $rt128156-lib-prefix.IO.add('RT128156'), to some temporary location, and then include that library path. This way each time the test is run the files in roast will not be changed. In Rakudo a similar pattern can be seen in t/02-rakudo/reproducible-builds.t