SystemTools: Use COMPILE_DEFINITIONS to pass platform tests
SystemTools: Use COMPILE_DEFINITIONS to pass platform tests

Replace use of COMPILE_FLAGS with COMPILE_DEFINITIONS for the
SystemTools.cxx source file property and spell out each definition on
its own line.

Change-Id: I213326b25fc7510107b78a8e233a3198862d9309

chuckatkins/KWSys,chuckatkins/KWSys,chuckatkins/KWSys,chuckatkins/KWSys