Merge pull request #2919 from dgovil/boost_python_clang15_fixes

Disable BOOST_UNORDERED_HAVE_PIECEWISE_CONSTRUCT for MacOS builds

(Internal change: 2317210)

build_scripts/build_usd.py

@@ -895,7 +895,14 @@ def InstallBoost_Helper(context, force, buildArgs):
             # Must specify toolset=clang to ensure install_name for boost
             # libraries includes @rpath
             b2_settings.append("toolset=clang")
-
+            #
+            # Xcode 15.3 (and hence Apple Clang 15) removed the global
+            # declaration of std::piecewise_construct which causes boost build
+            # to fail.
+            # https://developer.apple.com/documentation/xcode-release-notes/xcode-15_3-release-notes.
+            # A fix for the same is also available in boost 1.84:
+            # https://github.com/boostorg/container/commit/79a75f470e75f35f5f2a91e10fcc67d03b0a2160
+            b2_settings.append(f"define=BOOST_UNORDERED_HAVE_PIECEWISE_CONSTRUCT=0")
             if macOSArch:
                 b2_settings.append("cxxflags=\"{0}\"".format(macOSArch))
                 b2_settings.append("cflags=\"{0}\"".format(macOSArch))