[wasm] Fix alloc/dealloc size mismatch for WasmInstructionBuffer

On newer compilers the {operator delete} with explicit {size_t}
argument would be instantiated for {WasmInstructionBuffer} and used
in the destructor of {std::unique_ptr<WasmInstructionBuffer>}. The
{size_t} argument is wrong though, since the pointer actually points
to a {WasmInstructionBufferImpl} object.
The solution is to explicitly provide a {operator delete}, preventing
an implicitly generated {size_t} operator.

R=clemensh@chromium.org

Change-Id: I2cc22078d03a523121309bae94f5b612cb98e112
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1702613Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62737}

src/wasm/function-compiler.h

@@ -35,6 +35,10 @@ class WasmInstructionBuffer final {
 
   static std::unique_ptr<WasmInstructionBuffer> New();
 
+  // Override {operator delete} to avoid implicit instantiation of {operator
+  // delete} with {size_t} argument. The {size_t} argument would be incorrect.
+  void operator delete(void* ptr) { ::operator delete(ptr); }
+
  private:
   WasmInstructionBuffer() = delete;
   DISALLOW_COPY_AND_ASSIGN(WasmInstructionBuffer);