Fix warning in Mac rewarding unnecessary lambda capture (#4052)

Signed-off-by: Miguel Company <[email protected]>

test/blackbox/common/BlackboxTestsTransportSHM.cpp

@@ -116,16 +116,19 @@ TEST(SHM, IgnoreNonExistentSegment)
     // Create and quickly destroy several participants in several threads
 #ifdef _WIN32
     constexpr size_t num_threads = 1;
-    constexpr size_t num_parts = 2;
 #else
     constexpr size_t num_threads = 10;
-    constexpr size_t num_parts = 10;
 #endif  // _WIN32
     std::vector<std::thread> threads;
     for (size_t i = 0; i < num_threads; i++)
     {
-        threads.push_back(std::thread([num_parts]()
+        threads.push_back(std::thread([]()
                 {
+#ifdef _WIN32
+                    constexpr size_t num_parts = 2;
+#else
+                    constexpr size_t num_parts = 10;
+#endif  // _WIN32
                     for (size_t i = 0; i < num_parts; ++i)
                     {
                         PubSubWriter<Data1mbPubSubType> late_writer(TEST_TOPIC_NAME);