Attempt to make the external code generator test more robust on platforms where clang has difficulty cross compiling across bitness without extra flags.
Attempt to make the external code generator test more robust on
platforms where clang has difficulty cross compiling across bitness
without extra flags.

kgnk/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,kgnk/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,psuriana/Halide,kgnk/Halide,psuriana/Halide,psuriana/Halide,kgnk/Halide,psuriana/Halide,psuriana/Halide