Silence "may be used uninitialized" GCC warning

Helps gcc silence the warning about

```
warning: 'added' may be used uninitialized [-Wmaybe-uninitialized]
const IndexType offsetA0 = TransformedFeatureDimensions * added[0];
```

closes https://github.com/official-stockfish/Stockfish/pull/5950

No functional change

src/nnue/nnue_accumulator.cpp

@@ -25,13 +25,25 @@
 #include "../bitboard.h"
 #include "../position.h"
 #include "../types.h"
-#include "nnue_architecture.h"
 #include "network.h"
+#include "nnue_architecture.h"
 #include "nnue_common.h"
 #include "nnue_feature_transformer.h"
 
 namespace Stockfish::Eval::NNUE {
 
+#if defined(__GNUC__) && !defined(__clang__)
+    #define sf_assume(cond) \
+        do \
+        { \
+            if (!(cond)) \
+                __builtin_unreachable(); \
+        } while (0)
+#else
+    // do nothing for other compilers
+    #define sf_assume(cond)
+#endif
+
 namespace {
 
 template<Color                                     Perspective,
@@ -245,6 +257,12 @@ void update_accumulator_incremental(
         else
             assert(removed.size() <= added.size());
 
+        // Workaround compiler warning for uninitialized variables, replicated on
+        // profile builds on windows with gcc 14.2.0.
+        // TODO remove once unneeded
+        sf_assume(added.size() == 1 || added.size() == 2);
+        sf_assume(removed.size() == 1 || removed.size() == 2);
+
 #ifdef VECTOR
         auto* accIn =
           reinterpret_cast<const vec_t*>(&(computed.*accPtr).accumulation[Perspective][0]);