Add compilation test instead of VxWorks check

`<future>` is explicitly excluded for VxWork, because enabling it causes
compilation error when building tests (and causes some serious issues
when trying to naively work-arond this compilation problem). When
forcing `QT_FEATURE_cxx11_future` on VxWorks, failure occurs:

```
qtbase/src/corelib/thread/qthread.h:125:19: error: no matching function for call to 'invoke'
  125 |             (void)std::invoke(std::move(f), std::forward<decltype(largs)>(largs)...);
      |                   ^~~~~~~~~~~

[...]
qtbase/tests/auto/corelib/thread/qpromise/snippet_qpromise.cpp:32:45: note: in instantiation of function template specialization 'QThread::create<(lambda at qtbase/tests/auto/corelib/thread/qpromise/snippet_qpromise.cpp:32:52), QPromise<int>>' requested here
   32 |     QScopedPointer<QThread> thread(QThread::create([] (QPromise<int> promise) {
      |                                             ^
VSB/usr/h/public/type_traits:2720:7: note: candidate template ignored: substitution failure [with _Callable = remove_reference_t<(lambda at qtbase/tests/auto/corelib/thread/qpromise/snippet_qpromise.cpp:32:52) &>, _Types = <QPromise<int> &>]: no matching function for call to '_Call'
 2720 |         auto invoke(_Callable&& _Obj, _Types&&... _Args) noexcept(noexcept(_Invoker<_Callable, _Types...>::_Call(
      |              ^
 2721 |                 _STD forward<_Callable>(_Obj), _STD forward<_Types>(_Args)...)))
 2722 |         -> decltype(_Invoker<_Callable, _Types...>::_Call(
      |                     ~~~~~~~~
```

Instead of excluding cxx11_future on VxWorks explicitly, replace
condition with actual check which should pass in non-VxWorks 24.03 (or
older) standard libraries.

VxWorks in version 24.03 fails this test due to std::async improperly
forwards argument type to lambda, which causes compilation error when
argument type is a non-copiable value type. This is a problem in VxWorks
standard library, which could be fixed in future versions of this OS, so
keeping this as a test should unlock `<future>` header once it's fixed.

Pick-to: 6.7
Task-number: QTBUG-115777
Change-Id: Ic67df9be2e95dce999689eaea146f113017ab4f3
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 29 insertions, 1 deletions

diff --git a/src/corelib/configure.cmake b/src/corelib/configure.cmake
index 80e6d93193..18c09d2241 100644
--- a/src/corelib/configure.cmake
+++ b/src/corelib/configure.cmake
@@ -430,6 +430,34 @@ const auto backtrace = std::stacktrace::current();
     CXX_STANDARD 23
 )
 
+# <future>
+qt_config_compile_test(cxx_std_async_noncopyable
+    LABEL "std::async() NonCopyable"
+    CODE
+"// Calling std::async with lambda which takes non-copyable argument causes compilation error on
+// some platforms (VxWorks 24.03 and older with C++17-compatibility for example)
+#include <future>
+
+class NonCopyable {
+public:
+    NonCopyable(const NonCopyable&) = delete;
+    NonCopyable(NonCopyable&&) = default;
+
+    NonCopyable(int value)
+        :value (value)
+    {}
+
+    int value;
+};
+
+int main(int argc, char** argv) {
+    return std::async(
+        std::launch::deferred,
+        [](NonCopyable value) { return value.value; },
+        NonCopyable(argc - 1)).get();
+}
+")
+
 #### Features
 
 qt_feature("clock-gettime" PRIVATE
@@ -458,7 +486,7 @@ qt_feature("system-doubleconversion" PRIVATE
 )
 qt_feature("cxx11_future" PUBLIC
     LABEL "C++11 <future>"
-    CONDITION NOT VXWORKS
+    CONDITION TEST_cxx_std_async_noncopyable
 )
 qt_feature("cxx17_filesystem" PUBLIC
     LABEL "C++17 <filesystem>"