python3Packages.py3exiv2: fix build

[Ma27]

Motivation for this change

Recent boost versions name their python3 shared objects
boost_python3x rather than boost_python3.

See https://hydra.nixos.org/build/80712295
Addresses #45960

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Fits CONTRIBUTING.md.

---

[Mic92]

@GrahamcOfBorg build python3Packages.py3exiv2 python2Packages.py3exiv2

[GrahamcOfBorg]

Success on x86_64-darwin (full log)

Attempted: python3Packages.py3exiv2

The following builds were skipped because they don't evaluate on x86_64-darwin: python2Packages.py3exiv2

Partial log (click to expand)

reading manifest template 'MANIFEST.in'
writing manifest file 'src/py3exiv2.egg-info/SOURCES.txt'
running build_ext
copying build/lib.macosx-10.6-x86_64-3.6/libexiv2python.cpython-36m-darwin.so -> src

----------------------------------------------------------------------
Ran 0 tests in 0.000s

OK
/nix/store/rzwdhnsiac7k1794lsv4srwxjmcinx0i-python3.6-py3exiv2-0.4.0

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Attempted: python3Packages.py3exiv2

The following builds were skipped because they don't evaluate on x86_64-linux: python2Packages.py3exiv2

Partial log (click to expand)

reading manifest template 'MANIFEST.in'
writing manifest file 'src/py3exiv2.egg-info/SOURCES.txt'
running build_ext
copying build/lib.linux-x86_64-3.6/libexiv2python.cpython-36m-x86_64-linux-gnu.so -> src

----------------------------------------------------------------------
Ran 0 tests in 0.000s

OK
/nix/store/2a0g7vq2f85xjsn64yqwa3gyhm97spf4-python3.6-py3exiv2-0.4.0

[GrahamcOfBorg]

Success on aarch64-linux (full log)

Attempted: python3Packages.py3exiv2

The following builds were skipped because they don't evaluate on aarch64-linux: python2Packages.py3exiv2

Partial log (click to expand)

reading manifest template 'MANIFEST.in'
writing manifest file 'src/py3exiv2.egg-info/SOURCES.txt'
running build_ext
copying build/lib.linux-aarch64-3.6/libexiv2python.cpython-36m-aarch64-linux-gnu.so -> src

----------------------------------------------------------------------
Ran 0 tests in 0.000s

OK
/nix/store/wh9cxmm7yr5p33829iij3sqay3r9c0dr-python3.6-py3exiv2-0.4.0

[Mic92]

backport: 20d144b