8059131: sawindbg.dll is not compiled with /SAFESEH

Summary: Make variable SAFESEH_FLAG replaced with /SAFESEH link option.
Reviewed-by: mgronlun, sla

make/windows/makefiles/sa.make

@@ -111,7 +111,7 @@ SA_LFLAGS = $(SA_LD_FLAGS) -nologo -subsystem:console -machine:$(MACHINE)
 SA_LFLAGS = $(SA_LFLAGS) -map -debug
 !endif
 !if "$(BUILDARCH)" == "i486"
-SA_LFLAGS = $(SAFESEH_FLAG) $(SA_LFLAGS)
+SA_LFLAGS = /SAFESEH $(SA_LFLAGS)
 !endif
 
 SA_CFLAGS = $(SA_CFLAGS) $(MP_FLAG)