Mac: Enable Mach exception handler by default

src/trusted/service_runtime/sel_main.c

Index: src/trusted/service_runtime/sel_main.c
diff --git a/src/trusted/service_runtime/sel_main.c b/src/trusted/service_runtime/sel_main.c
index 2caf1bea98ab475f5208cfe394c6da137e840bee..fdfb85f05b1fc7d206a21ea4fc5eb3309dd2fe71 100644
--- a/src/trusted/service_runtime/sel_main.c
+++ b/src/trusted/service_runtime/sel_main.c
@@ -485,10 +485,6 @@ int NaClSelLdrMain(int argc, char **argv) {
 #elif NACL_LINUX
     /* NaCl's signal handler is always enabled on Linux. */
 #elif NACL_OSX
-    if (!NaClInterceptMachExceptions()) {
-      fprintf(stderr, "ERROR setting up Mach exception interception.\n");
-      return -1;
-    }
 #else
 # error Unknown host OS
 #endif
@@ -496,6 +492,12 @@ int NaClSelLdrMain(int argc, char **argv) {
   if (NACL_LINUX) {
     handle_signals = 1;
   }
+#if NACL_OSX
+  if (!NaClInterceptMachExceptions()) {
+    fprintf(stderr, "ERROR setting up Mach exception interception.\n");
+    return -1;
+  }
+#endif
 
   errcode = LOAD_OK;
 
@@ -534,7 +536,9 @@ int NaClSelLdrMain(int argc, char **argv) {
   }
 
   if (handle_signals) {
+#if NACL_LINUX
     NaClSignalHandlerInit();
+#endif
   } else {
     /*
      * Patch the Windows exception dispatcher to be safe in the case