devel/onetbb: fix build on powerpc*

/usr/bin/c++ -DTBBMALLOC_BUILD -DTBB_USE_ITT_NOTIFY -I/wrkdirs/usr/ports/devel/onetbb/work/oneTBB-2021.3.0/src/tbbmalloc/../../include -O2 -pipe -fstack-protector-strong -fno-strict-aliasing -O2 -pipe -fstack-protector-strong -fno-strict-aliasing -fPIC -fno-rtti -fno-exceptions -pthread -std=c++11 -MD -MT src/tbbmalloc/CMakeFiles/tbbmalloc.dir/frontend.cpp.o -MF src/tbbmalloc/CMakeFiles/tbbmalloc.dir/frontend.cpp.o.d -o src/tbbmalloc/CMakeFiles/tbbmalloc.dir/frontend.cpp.o -c /wrkdirs/usr/ports/devel/onetbb/work/oneTBB-2021.3.0/src/tbbmalloc/frontend.cpp
/wrkdirs/usr/ports/devel/onetbb/work/oneTBB-2021.3.0/src/tbbmalloc/frontend.cpp:829:30: error: use of undeclared identifier 'getSmallObjectIndex'

unsigned int index = getSmallObjectIndex( size );