OCIO : Use boost::shared_ptr rather than tr1::shared_ptr.

This makes our build compatible with Maya.

build/buildOCIO.sh

@@ -9,7 +9,13 @@ export LD_LIBRARY_PATH=$BUILD_DIR/lib
 mkdir -p $BUILD_DIR/doc/licenses
 cp LICENSE $BUILD_DIR/doc/licenses/openColorIO
 
-cmake -DCMAKE_INSTALL_PREFIX=$BUILD_DIR -DPYTHON=$BUILD_DIR/bin/python -DOCIO_BUILD_TRUELIGHT=OFF -DOCIO_BUILD_APPS=OFF -DOCIO_BUILD_NUKE=OFF
+# By default, OCIO will use tr1::shared_ptr. But Maya (2015 and 2016 at least)
+# ships with a libOpenColorIO built using boost::shared_ptr instead. We'd like
+# Gaffer's default packages to be useable in Maya, so we pass OCIO_USE_BOOST_PTR=1
+# to match Maya's build. Even though both Gaffer and Maya respect the VFXPlatform
+# 2016 by using OCIO 1.0.9, this is an example of where the platform is under
+# specified, and we must go the extra mile to get compatibility.
+cmake -DCMAKE_INSTALL_PREFIX=$BUILD_DIR -DPYTHON=$BUILD_DIR/bin/python -DOCIO_USE_BOOST_PTR=1 -DOCIO_BUILD_TRUELIGHT=OFF -DOCIO_BUILD_APPS=OFF -DOCIO_BUILD_NUKE=OFF
 make clean && make -j 4 && make install
 
 mkdir -p $BUILD_DIR/python