[wasm][fuzzer] Fix compilation error on gcc

template specialisations must be defined
outside of class body to prevent the following compilation error:

error: explicit specialization in non-namespace scope

Change-Id: Ic4b74a28cd21d96991ad784fbd3c598668ffc476
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3129881Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/main@{#76591}

test/fuzzer/wasm-compile.cc

@@ -84,21 +84,22 @@ class DataRange {
     data_ += num_bytes;
     return result;
   }
-
-  template <>
-  bool get() {
-    // The general implementation above is not instantiable for bool, as that
-    // would cause undefinied behaviour when memcpy'ing random bytes to the
-    // bool. This can result in different observable side effects when invoking
-    // get<bool> between debug and release version, which eventually makes the
-    // code output different as well as raising various unrecoverable errors on
-    // runtime.
-    // Hence we specialize get<bool> to consume a full byte and use the least
-    // significant bit only (0 == false, 1 == true).
-    return get<uint8_t>() % 2;
-  }
 };
 
+// Explicit specialization must be defined outside of class body.
+template <>
+bool DataRange::get() {
+  // The general implementation above is not instantiable for bool, as that
+  // would cause undefinied behaviour when memcpy'ing random bytes to the
+  // bool. This can result in different observable side effects when invoking
+  // get<bool> between debug and release version, which eventually makes the
+  // code output different as well as raising various unrecoverable errors on
+  // runtime.
+  // Hence we specialize get<bool> to consume a full byte and use the least
+  // significant bit only (0 == false, 1 == true).
+  return get<uint8_t>() % 2;
+}
+
 ValueType GetValueType(uint32_t num_types, DataRange* data,
                        bool liftoff_as_reference) {
   constexpr ValueType types[] = {