vmstruct symbols is not exported under OS X

the /^gHotSpotVM/ won’t match anything since exported C symbols start with an underscore:

nm -Uj build/bsd/bsd_amd64_compiler2/product/vmStructs.o | awk '/^gHotSpotVM/ { print $1 } ' | wc -l
        0

nm -Uj build/bsd/bsd_amd64_compiler2/product/vmStructs.o | awk '/gHotSpotVM/ { print $1 } ' | wc -l
       24