Add diagnostics to failing Clipboard test and skip on non-GTK

[jonahgraham]

This records additional information about the state of the remote process. This will only hard fail on Linux as we have seen test pass on Linux, and Linux is the primary target as the Clipboard is under development on Linux only now for GTK4 work.

Part of #2553

[github-actions]

Test Results

  111 files  ±0    111 suites  ±0   10m 54s ⏱️ - 1m 39s
4 526 tests  - 1  4 511 ✅  - 1  14 💤 ±0  1 ❌ +1 
  274 runs  ±0    273 ✅ ±0   1 💤 ±0  0 ❌ ±0 

For more details on these failures, see this check.

Results for commit bdf184b. ± Comparison against base commit 87fa834.

This pull request removes 1 test.

org.eclipse.swt.tests.junit.Test_org_eclipse_swt_dnd_Clipboard ‑ Unknown test

♻️ This comment has been updated with latest results.

[iloveeclipse]

@jonahgraham : the four failing tests are known, see #2516

Do you plan to cotinue working on this PR or can it be merged "as is"?

[iloveeclipse]

Just rebased on latest master with the workaround for Windows GHA test fails.

[jonahgraham]

Do you plan to cotinue working on this PR or can it be merged "as is"?

It can be merged now, the build hadn't finished before my day ended on Friday. So I will merge now.

Just rebased on latest master with the workaround for Windows GHA test fails.

Thanks

There is a new unrelated failure:

test_setUrl_remote_with_post[browser flags: 524,288] (org.eclipse.swt.tests.junit.Test_org_eclipse_swt_browser_Browser) failed

I assume this is flaky and I can ignore it for now (I don't have time/ability to fix it and I am pretty sure it is unrelated to my change). Let me know if you would like me to do anything else with it.

[iloveeclipse]

There is a new unrelated failure:

test_setUrl_remote_with_post[browser flags: 524,288] (org.eclipse.swt.tests.junit.Test_org_eclipse_swt_browser_Browser) failed

See #2561

[jonahgraham]

https://download.eclipse.org/eclipse/downloads/drops4/I20250930-1800/testResults.php shows no failures - but see #2126 (comment) which I quote here for those following along:

https://download.eclipse.org/eclipse/downloads/drops4/I20250930-1800/testResults.php shows the new test passes on GTK3, but fails (but marked as skipped, so no disruption yet) on win/mac. Clearly more work needed on the tests.