Allow undefined BACKTRACE_* but emit a compiler warning.

stepmania/src/archutils/Unix/CrashHandler.cpp

@@ -374,8 +374,15 @@ static void do_backtrace(void **buf, size_t size)
     unsigned i;
     for (i=0; frame && frame->linkReg && i<size; ++i, frame=frame->stackPointer)
         buf[i] = frame->linkReg;
+    i = (i == size ? size - 1 : i);
     buf[i] = NULL;
 }
+#else
+#warning Undefined BACKTRACE_METHOD_*
+static void do_backtrace(void **buf, size_t size)
+{
+    buf[0] = NULL;
+}
 #endif
 
 

stepmania/src/archutils/Unix/CrashHandlerChild.cpp

@@ -251,7 +251,14 @@ void BacktraceNames::FromAddr( void *p )
     }
 }
 #else
-#error BACKTRACE_LOOKUP_METHOD_* required
+#warning Undefined BACKTRACE_LOOKUP_METHOD_*
+void BacktraceNames::FromAddr( void *p )
+{
+    Address = long(p);
+    Offset = 0;
+    Symbol = "";
+    File = "";
+}
 #endif