Running "ant jar-checksums" on Windows alters line endings on .sha1 files [LUCENE-7464]

On a Windows machine, I applied a patch to a fresh master checkout that changed the version of a component managed by Ivy. Then I ran "ant jar-checksums" to calculate a new sha1 checksum for the changed jar. A very large number of checksum files then mentioned line ending changes when I ran "git status".

IRC discussion:
```
12:58 <@elyograg> i guess jar-checksums shouldn't be run on windows. A whole
bunch of checksums appear to have had their line endings
changed.
13:02 <@elyograg> I expected only one checksum to change.
13:04 <@hoss> elyograg: that's odd ... i thought the checksum generating code
was done by ant and didn't depend on native line endings ... i
would definitely raise a jira
```

---
Migrated from [LUCENE-7464](https://issues.apache.org/jira/browse/LUCENE-7464) by Shawn Heisey (@elyograg)

Start by locating the build target behind `ant jar-checksums` and the code or configuration that writes the `.sha1` files. Reproduce the command on Windows and inspect the resulting `git status`; done means only the checksum for the changed JAR differs, without unrelated line-ending changes.

Written by the indexing model from the issue text.