sim: m68hc11: warn when emul_write fails

Not sure what we should do here when this fails, so just emit a warning
for now to satisfy unused result compiler warnings.  We can see if any
users actually notice here.

sim/m68hc11/ChangeLog

@@ -1,3 +1,8 @@
+2021-05-06  Mike Frysinger  <vapier@gentoo.org>
+
+	* emulos.c: Include errno.h & stdio.h.
+	(emul_write): Print a warning when the write fails.
+
 2021-05-04  Mike Frysinger  <vapier@gentoo.org>
 
 	* dv-m68hc11.c (struct m68hc11cpu): Change attach_size to unsigned int.

sim/m68hc11/emulos.c

@@ -23,6 +23,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 #endif
 
 #ifndef WIN32
+#include <errno.h>
+#include <stdio.h>
 #include <sys/types.h>
 #include <sys/time.h>
 
@@ -103,8 +105,9 @@ emul_write (sim_cpu *cpu)
   while (size)
     {
       uint8 val = memory_read8 (cpu, addr);
-        
+
-      write(0, &val, 1);
+      if (write (0, &val, 1) != 1)
+	printf ("write failed: %s\n", strerror (errno));
       addr ++;
       size--;
     }