arm: move trace dump to crash handler

arm/stdlib.cc

@@ -7,14 +7,19 @@
 #include "timer.h"
 #include "uart.h"
 
+#ifndef SBRK_STATS
+#define SBRK_STATS 0
+#endif
+
 extern unsigned char _heap_begin, _heap_end;
 
 namespace {
+[[maybe_unused]]
 void LogStats(unsigned char* heap) {
     char number[] = "00000000\r\n";
-    UartWriteBlocking("Program break now at 0x");
+    UartWriteCrash("Program break now at 0x");
     itoa(reinterpret_cast<int>(heap), number);
-    UartWriteBlocking(number);
+    UartWriteCrash(number);
 }
 }  // namespace
 
@@ -22,11 +27,13 @@ extern "C" void* _sbrk(int increment) {
     static unsigned char* heap = &_heap_begin;
     unsigned char* prev_heap = heap;
     if (heap + increment >= &_heap_end) {
-        UartWriteBlocking("Heap overflow!\r\n");
+        UartWriteCrash("Heap overflow!\r\n");
         return reinterpret_cast<void*>(-1);
     }
     heap += increment;
+#if SBRK_STATS
     LogStats(heap);
+#endif
     return prev_heap;
 }