build: fix preprocessor guards
build: fix preprocessor guards

gdk_utils.mx:506:7: error: "HAVE_GLOBALMEMORYSTATUS" is not defined

use defined() to check for this (as was the intention)

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb