Merge bitcoin/bitcoin#25436: build: GCC-12 build improvements

880d4aaf81f3d5d7fbb915905c2e61b816a6a747 build: use BOOST_NO_CXX98_FUNCTION_BASE to suppress warnings (fanquake)
1bdbbbdc46c4e50bf07bc362e7e391ea1a53ea2f build: suppress array-bounds errors in libxkbcommon (fanquake)

Pull request description:

  2 changes to better support building with GCC 12, which out of the box, is currently broken if you want to build using depends.
  Prevent `-Warray-bounds` errors when building libxkbcommon. i.e:
  ```bash
  src/xkbcomp/ast-build.c:82:27: error: array subscript 'ExprDef[0]' is partly outside array bounds of 'unsigned char[32]' [-Werror=array-bounds]
     82 |     expr->expr.value_type = type;
        |     ~~~~~~~~~~~~~~~~~~~~~~^~~~~~
  src/xkbcomp/ast-build.c:75:21: note: object of size 32 allocated by 'malloc'
     75 |     ExprDef *expr = malloc(size);
        |                     ^~~~~~~~~~~~
  ```

  It might be the case that these would be fixed by updating the
  package, but that would also require installing new build tools (meson),
  as well as potentially more dependencies (wayland), and it'd need
  testing with Qt. For now, just turn the errors into wanrings.

  Define `BOOST_NO_CXX98_FUNCTION_BASE` to prevent GCC warning about the use of `std::unary_function`. i.e:
  ```bash
  /bitcoin/depends/aarch64-unknown-linux-gnu/include/boost/container_hash/hash.hpp:131:33:
  warning: 'template<class _Arg, class _Result> struct std::unary_function' is deprecated [-Wdeprecated-declarations]
    131 |         struct hash_base : std::unary_function<T, std::size_t> {};
        |                                 ^~~~~~~~~~~~~~
  In file included from /usr/include/c++/12/bits/unique_ptr.h:37,
                   from /usr/include/c++/12/memory:76,
                   from ./init.h:10,
                   from init.cpp:10:
  /usr/include/c++/12/bits/stl_function.h:117:12: note: declared here
    117 |     struct unary_function
  ```

  Boost `container_hash` (included via functional -> multi_index) uses
  [`std::unary_function`, which was deprecated in C++11](https://en.cppreference.com/w/cpp/utility/functional/unary_function), and "removed" in
  C++17. It's use causes warnings with newer compilers, i.e GCC 12.1.

  Use the MACRO outlined in https://github.com/boostorg/container_hash/issues/22, and added to Boost Config for GCC 12 in https://github.com/boostorg/config/pull/430, to prevent it's use.

  [BOOST_NO_CXX98_FUNCTION_BASE](https://www.boost.org/doc/libs/master/libs/config/doc/html/boost_config/boost_macro_reference.html):
  > The standard library no longer supports std::unary_function and std::binary_function.
  > They were deprecated in C++11 and is removed from C++14.

  Guix Build (x86_64):
  ```bash

  ```

  Guix Build (arm64):
  ```bash

  ```

ACKs for top commit:
  laanwj:
    Code review ACK 880d4aaf81f3d5d7fbb915905c2e61b816a6a747

Tree-SHA512: 10c4679c3eb788e9279acc4960731c55ae1568bd3df525d3c46f97d8b0319e7d8450b1638b6777d98111b5991dba5c787e95d80b1ac932e0b4779d4b8e74875e

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