[UnitCL] Fix C11Atomics_73_*, C11Atomics_74_*, C11Atomics_75_*

These tests test atomic_compare_exchange_weak_explicit which is allowed
to fail for no clear reason. The test tries to account for this by
detecting output differences, using that to set a weak_exchange_failed
boolean, and using that weak_exchange_failed boolean to detect where the
result of atomic_compare_exchange_weak_explicit does not match
expectations. That is, in output_reference, it does:

          if (value == expected_values[success_index]) {
            weak_exchange_failed = true;
            return true;
          }

Then, bool_output_reference is:

        [success_index, weak_exchange_failed](size_t index) {
          return index == success_index && !weak_exchange_failed;
        };

The problem here is that bool_output_reference is constructed capturing
weak_exchange_failed by value, so it will never pick up the updated
value even if it was detected that the weak exchange had failed. To fix
this, capture it by reference instead.

source/cl/test/UnitCL/source/C11Atomics.cpp

@@ -2365,7 +2365,7 @@ class WeakGlobalSingle : public C11AtomicTestBase {
       return desired_values[index];
     };
     kts::Reference1D<cl_int> bool_output_reference =
-        [success_index, weak_exchange_failed](size_t index) {
+        [success_index, &weak_exchange_failed](size_t index) {
           return index == success_index && !weak_exchange_failed;
         };