Cast away [[nodiscard]] values in runtime support checks

Test calls in Q{SystemSemaphore,SharedMemory}*::runtimeSupportCheck()
are commented to be sure to fail, so the return is irrelevant.
Suppresses warnings from CodeChecker.

Change-Id: I2ac6ccb8d96a169229dcf24a744015fb9d414c74
Reviewed-by: Marc Mutz <marc.mutz@qt.io>

src/corelib/ipc/qsharedmemory_posix.cpp

@@ -27,7 +27,7 @@ using namespace QtIpcCommon;
 bool QSharedMemoryPosix::runtimeSupportCheck()
 {
     static const bool result = []() {
-        shm_open("", 0, 0);         // this WILL fail
+        (void)shm_open("", 0, 0);         // this WILL fail
         return errno != ENOSYS;
     }();
     return result;

src/corelib/ipc/qsharedmemory_systemv.cpp

@@ -36,7 +36,7 @@ bool QSharedMemorySystemV::runtimeSupportCheck()
         return false;
 #endif
     static const bool result = []() {
-        shmget(IPC_PRIVATE, ~size_t(0), 0);     // this will fail
+        (void)shmget(IPC_PRIVATE, ~size_t(0), 0);     // this will fail
         return errno != ENOSYS;
     }();
     return result;

src/corelib/ipc/qsystemsemaphore_systemv.cpp

@@ -40,7 +40,7 @@ bool QSystemSemaphoreSystemV::runtimeSupportCheck()
         return false;
 #endif
     static const bool result = []() {
-        semget(IPC_PRIVATE, -1, 0);     // this will fail
+        (void)semget(IPC_PRIVATE, -1, 0);     // this will fail
         return errno != ENOSYS;
     }();
     return result;