Work around boost failure to build in clang 15

[geoffrey4444]

Proposed changes

Workaround for boost not building with clang 15: adds -D_HAS_AUTO_PTR_ETC=0 to CMAKE_CXXX_FLAGS if clang version >= 15.0.0. This fix is necessary to build with latest Xcode/AppleClang.

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Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

Further comments

[geoffrey4444]

I use if/elseif here, even though it duplicates a line, to avoid lines over 80 characters. I tried continuing the if line with , but make complained

[wthrowe]

I believe CMake ignores newlines outside of strings (except as generic whitespace), so you should be able to wrap it just like C++.

(To any other readers: The previous comment contains a backslash before the last comma, but GitHub isn't displaying it.)

[nilsvu]

Add this to SetupBoost.cmake please, to the boost target using target_compile_definitions.

[geoffrey4444]

Ready for another look when you get a chance...thanks for the reviews! It's such a short PR that I squashed immediately.

[nilsvu]

This only became a problem with recent versions of boost (the code builds fine with boost 1.74 and clang 15 in the container, though I don't see an obvious reason why). It is fixed in boost 1.83. Therefore I suggest to add the condition BOOST_VERSION VERSION_LESS 1.83.0.

[geoffrey4444]

This only became a problem with recent versions of boost (the code builds fine with boost 1.74 and clang 15 in the container, though I don't see an obvious reason why). It is fixed in boost 1.83. Therefore I suggest to add the condition BOOST_VERSION VERSION_LESS 1.83.0.

Note that brew has not yet updated boost to 1.83.0, so until they do, this workaround still matters for macOS users running the latest AppleClang

[nilsvu]

Note that GREATER_EQUAL also exists, and this could also be combined with the above if (not requesting this).

[nilsvu]

Thanks for fixing this @geoffrey4444 !