Enable VM fault message by default on Linux

This option was disabled by default to address issues writing to stderr
in Windows applications. The lack of an error message for memory access
faults is confusing to users, however.

Enable the error message by default on Linux only.

Change-Id: I1f44ba42362f8874abdc7c8e63ddd54a855b5394

runtime/hsa-runtime/core/util/flag.h

@@ -61,7 +61,7 @@ class Flag {
     check_flat_scratch_ = (var == "1") ? true : false;
 
     var = os::GetEnvVar("HSA_ENABLE_VM_FAULT_MESSAGE");
-    enable_vm_fault_message_ = (var == "1") ? true : false;
+    enable_vm_fault_message_ = (var == "0") ? false : true;
 
     var = os::GetEnvVar("HSA_ENABLE_INTERRUPT");
     enable_interrupt_ = (var == "0") ? false : true;