Fix build_daemon modify while building.

[davidmorgan]

Fix #4268

This is a regression from a few versions back: the "was it actually modified" check was changed during the refactor to use the readerWriter in buildSeries which can have a cache, which fails because the cache refuses to invalidate a file while there are pending writes. (Which is good! It would have corrupted the build).

Revert to using the one without a cache instead.

I tried to come up with an e2e test for it but the timing is awkward, I didn't manage to repro in a test; it repros easily enough manually, so confirmed the fix that way.

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:build	4.0.2	already published at pub.dev
package:build_config	1.2.0	already published at pub.dev
package:build_daemon	4.1.0	already published at pub.dev
package:build_modules	5.1.1	already published at pub.dev
package:build_runner	2.10.2	ready to publish	build_runner-v2.10.2
package:build_test	3.5.2	ready to publish	build_test-v3.5.2
package:build_web_compilers	4.4.1	already published at pub.dev
package:scratch_space	1.2.0	already published at pub.dev

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.

[github-actions]

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