fix build against libstdc++ 12

[jvgutierrez]

While attempting to compile katran on Debian Bullseye and Bookworm I've realized that it compiled as expected on Bullseye with clang-13 but failed on Bookworm with the same compiler issuing the following error:

/tmp/fbcode_builder_getdeps-ZrootZkatranZbuildZfbcode_builder-root/repos/git.luolix.top-facebookincubator-katran.git/katran/lib/BpfLoader.cpp:46:25:
 error: implicit instantiation of undefined template 'std::array<char, 128>'
 std::array<char, 128> buf{};

Debugging the issue with clang++ -H I've noticed that BpfLoader.h:21: #include <unordered_map>
implicitly includes array when using libstdc++ 10:

.. /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/unordered_map
... /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/hashtable.h
.... /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/hashtable_policy.h
..... /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/tuple
...... /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/array
...... /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/uses_allocator.h
...... /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/invoke.h
..... /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/limits
... /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/unordered_map.h

but this doesn't happen with libstdc++ 12:

.. /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/unordered_map
... /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/hashtable.h
.... /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/hashtable_policy.h
..... /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/tuple
...... /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/uses_allocator.h
.... /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/enable_special_members.h
... /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/unordered_map.h

Adding a explicit #include <array> fixes the error

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[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. If you'd still like this PR merged, please comment on the PR, make sure you've addressed reviewer comments, and rebase on the latest main. Thank you for your contributions!

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[jdoupe]

This is still an issue (and a simple fix).