test: Fix fuzzer compilation on macOS #19562

fixes #19557

Before the fix:

➜  bitcoin git:(fix-fuzzer-macos) make
Making all in src
  CXX      test/fuzz/addition_overflow-addition_overflow.o
In file included from test/fuzz/addition_overflow.cpp:7:
./test/fuzz/util.h:335:13: error: no matching function for call to 'AdditionOverflow'
        if (AdditionOverflow((uint64_t)fuzzed_file->m_offset, random_bytes.size())) {
            ^~~~~~~~~~~~~~~~
./test/fuzz/util.h:201:16: note: candidate template ignored: deduced conflicting types for parameter 'T' ('unsigned long long' vs. 'unsigned long')
NODISCARD bool AdditionOverflow(const T i, const T j) noexcept
               ^
./test/fuzz/util.h:346:13: error: no matching function for call to 'AdditionOverflow'
        if (AdditionOverflow(fuzzed_file->m_offset, n)) {
            ^~~~~~~~~~~~~~~~
./test/fuzz/util.h:201:16: note: candidate template ignored: deduced conflicting types for parameter 'T' ('long long' vs. 'long')
NODISCARD bool AdditionOverflow(const T i, const T j) noexcept
               ^

After the fix:

➜  bitcoin git:(fix-fuzzer-macos) ./configure --enable-fuzz --with-sanitizers=fuzzer,address,undefined CC=/usr/local/opt/llvm/bin/clang CXX=/usr/local/opt/llvm/bin/clang++ --disable-asm && make clean && make -j5
...
...
  CXXLD    test/fuzz/uint256_deserialize
Making all in doc/man
make[1]: Nothing to be done for `all'.
make[1]: Nothing to be done for `all-am'.

This PR is following the advice of @practicalswift here: #19557 (comment)

review ACK c8992e89594a54edf283e4916f794475070b5114

ACK c8992e89594a54edf283e4916f794475070b5114 - tested that compiling works on macOS.

In future, if you're cherry-picking / contributing somebody else's patch, adding a Co-authored-by: other contributor is appreciated.