[foreign-jextract] RFR: Fix some tests failing jextract on Windows

[Athijegannathan Sundararajan]

On Tue, 25 Aug 2020 12:21:37 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> Hi,
> 
> This PR fixes some tests that were failing on Windows;
> 
> 1. The new test for `long double` layouts gives a false positive on Windows for the `double` layout, since both are 64
> bits. I've added another check to see that the `long double` layout is actually 128 bits. (Since it's 64 bits on
> Windows, it would be allowed there, but it behaves the same as `double` so that should be fine).  2. A test using
> vsprintf was failing. It was depending on the default library to load the standard c library function, but this doesn't
> work reliably on Windows. I've put a wrapper around the vsprintf function, and called that instead. When building this
> wrapper the correct vsprintf is picked up.  Thanks, Jorn

Marked as reviewed by sundar (Committer).

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PR: https://git.openjdk.java.net/panama-foreign/pull/293