sim: add checks to core headers to prevent incorrect common building

Some of the core sim headers rely on the SIM_AC_OPTION_BITSIZE macro
which can change the size of core types.  Since these haven't been
unified across ports, add checks to make sure they aren't accidentally
included when building for all ports.  This caught the sim-load file
using poisoned headers that it didn't actually need.

sim/common/sim-config.h

@@ -23,6 +23,9 @@
 #ifndef SIM_CONFIG_H
 #define SIM_CONFIG_H
 
+#ifdef SIM_COMMON_BUILD
+#error "This header is unusable in common builds due to reliance on SIM_AC_OPTION_BITSIZE"
+#endif
 
 /* Host dependant:
 

sim/common/sim-load.c

@@ -27,12 +27,11 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <stdlib.h>
 #include <time.h>
 
-#include "sim-basics.h"
 #include "bfd.h"
-#include "sim-utils.h"
 
 #include "sim/callback.h"
 #include "sim/sim.h"
+#include "sim-utils.h"
 
 static void eprintf (host_callback *, const char *, ...);
 static void xprintf (host_callback *, const char *, ...);

sim/common/sim-types.h

@@ -23,6 +23,10 @@
 #ifndef SIM_TYPES_H
 #define SIM_TYPES_H
 
+#ifdef SIM_COMMON_BUILD
+#error "This header is unusable in common builds due to reliance on SIM_AC_OPTION_BITSIZE"
+#endif
+
 #include <stdint.h>
 
 /* INTEGER QUANTITIES: