error: unknown target CPU 'i386' for the boost b2 build using architecture=x86 address-model=32

[anonymous]

Trying to build boost 1.52 for 32 bit architecture on OS X 10.7.5, using clang:

./b2 toolset=clang cxxflags="-std=c++11 -stdlib=libc++" linkflags="-stdlib=libc++" architecture=x86 address-model=32

Get a lot of errors of this type:

    "clang++" -x c++ -O3 -std=c++11 -stdlib=libc++ -O3 -finline-functions -Wno-inline -Wall -march=i386 -DBOOST_ALL_DYN_LINK=1 -DBOOST_ALL_NO_LIB=1 -DDATE_TIME_INLINE -DNDEBUG -I"." -c -o "bin.v2/libs/date_time/build/clang-darwin-4.2.1/release/address-model-32/architecture-x86/threading-multi/gregorian/greg_month.o" "libs/date_time/src/gregorian/greg_month.cpp"

...failed clang-darwin.compile.c++ bin.v2/libs/date_time/build/clang-darwin-4.2.1/release/address-model-32/architecture-x86/threading-multi/gregorian/greg_month.o...
clang-darwin.compile.c++ bin.v2/libs/date_time/build/clang-darwin-4.2.1/release/address-model-32/architecture-x86/threading-multi/gregorian/greg_weekday.o
error: unknown target CPU 'i386'