RFR: 6914: Fix windows check formatting script

Fri Oct 2 17:49:34 UTC 2020

On Fri, 2 Oct 2020 17:23:45 GMT, Jean-Philippe Bempel <github.com+4610701+jpbempel at openjdk.org> wrote:

> because mvn is itself a script we need to call with call command
> to get control back to the main script

Updated the bug with some additional thoughts:
https://bugs.openjdk.java.net/browse/JMC-6914

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PR: https://git.openjdk.java.net/jmc/pull/114