fix build on GCC13

[NicolasDerumigny]

Building with GCC13.1.1 does not finish and crashed with error:

../../../../../submodules/qemu/tcg/plugins/cpp/coverage.cpp: In member function ‘void plugin_coverage::dump_symbol_coverage(symbol&, std::unordered_map<long unsigned int, long unsigned int>&)’:
../../../../../submodules/qemu/tcg/plugins/cpp/coverage.cpp:77:32: error: possibly dangling reference to a temporary [-Werror=dangling-reference]
   77 |             const instruction& i = get_instruction(i_pc, std::move(cs_inst));
      |                                ^
../../../../../submodules/qemu/tcg/plugins/cpp/coverage.cpp:77:51: note: the temporary was destroyed at the end of the full expression ‘plugin::get_instruction(i_pc, std::unique_ptr<cs_insn, void (*)(cs_insn*)>((* & std::move<unique_ptr<cs_insn, void (*)(cs_insn*)>&>(cs_inst))))’
   77 |             const instruction& i = get_instruction(i_pc, std::move(cs_inst));
      |                                    ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
ninja: build stopped: subcommand failed.

This fixes the issue.

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