apacheGH-41463: [C++] Skip TestConcurrentFillFromScalar for platforms…

… without threading support (apache#41461)

### Rationale for this change

See apache#41463 and apache#40237 (comment)

### What changes are included in this PR?

Skip test for platforms that have no threading support.

### Are these changes tested?

Change is test.

### Are there any user-facing changes?

None.

* GitHub Issue: apache#41463

Authored-by: Ruoxi Sun <zanmato1984@gmail.com>
Signed-off-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>

cpp/src/arrow/array/array_test.cc

@@ -827,6 +827,9 @@ TEST_F(TestArray, TestFillFromScalar) {
 // GH-40069: Data-race when concurrent calling ArraySpan::FillFromScalar of the same
 // scalar instance.
 TEST_F(TestArray, TestConcurrentFillFromScalar) {
+#ifndef ARROW_ENABLE_THREADING
+  GTEST_SKIP() << "Test requires threading support";
+#endif
   for (auto type : TestArrayUtilitiesAgainstTheseTypes()) {
     ARROW_SCOPED_TRACE("type = ", type->ToString());
     for (auto seed : {0u, 0xdeadbeef, 42u}) {