Wrap Char in array to avoid pointer arithmetic (fmtlib#3695)

This resolves the following finding reported by Coverity Static Analysis
v2023.6.1 on line 1964 of fmt/include/fmt/format.h:

  ptr_arith: Using &v as an array. This might corrupt or misinterpret
             adjacent memory locations.

include/fmt/format.h

@@ -1958,11 +1958,12 @@ auto write_escaped_string(OutputIt out, basic_string_view<Char> str)
 
 template <typename Char, typename OutputIt>
 auto write_escaped_char(OutputIt out, Char v) -> OutputIt {
+  Char v_array[1] = {v};
   *out++ = static_cast<Char>('\'');
   if ((needs_escape(static_cast<uint32_t>(v)) && v != static_cast<Char>('"')) ||
       v == static_cast<Char>('\'')) {
     out = write_escaped_cp(
-        out, find_escape_result<Char>{&v, &v + 1, static_cast<uint32_t>(v)});
+        out, find_escape_result<Char>{v_array, v_array + 1, static_cast<uint32_t>(v)});
   } else {
     *out++ = v;
   }