RFR: 8302693: TestDocComments fails on Windows

Thu Feb 16 21:50:52 UTC 2023

TestDocComments fails on Windows because it's trying to `typedef` `size_t` with the type `unsigned long`, which is different from the type Windows uses for `size_t`: `unsigned long long`.

Using the latter works accross supported platforms though.

(I've also amended the testing framework code to print out jextract output in case of a failure)

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Commit messages:
 - fix win failure of TestDocComments

Changes: https://git.openjdk.org/jextract/pull/106/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=106&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-8302693
  Stats: 3 lines in 3 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jextract/pull/106.diff
  Fetch: git fetch https://git.openjdk.org/jextract pull/106/head:pull/106

PR: https://git.openjdk.org/jextract/pull/106