Add debug support for build.opt (#8637)

Add support to have different build option comment blocks
for debug and production builds.

Updated example esp8266/HwdtStackDump to use build.opt

libraries/esp8266/examples/HwdtStackDump/HwdtStackDump.ino

@@ -47,8 +47,6 @@ extern "C" {
 ////////////////////////////////////////////////////////////////////
 
 void setup(void) {
-  WiFi.persistent(false);  // w/o this a flash write occurs at every boot
-  WiFi.mode(WIFI_OFF);
   Serial.begin(115200);
   delay(20);  // This delay helps when using the 'Modified Serial monitor' otherwise it is not needed.
   Serial.println();
@@ -56,16 +54,20 @@ void setup(void) {
   Serial.println(F("The Hardware Watchdog Timer Demo is starting ..."));
   Serial.println();
 
+#ifdef DEMO_THUNK
   // This allows us to test dumping a BearSSL stack after HWDT.
   stack_thunk_add_ref();
   thunk_ets_uart_printf("Using Thunk Stack to print this line.\n\n");
+#endif
 
+#ifdef DEMO_WIFI
   // We don't need this for this example; however, starting WiFi uses a little
   // more of the SYS stack.
   WiFi.mode(WIFI_STA);
   WiFi.begin(ssid, password);
   Serial.println(F("A WiFi connection attempt has been started."));
   Serial.println();
+#endif
 
   // #define DEMO_NOEXTRA4K
 #ifdef DEMO_NOEXTRA4K

libraries/esp8266/examples/HwdtStackDump/HwdtStackDump.ino.globals.h

@@ -0,0 +1,51 @@
+/*@create-file:build.opt:debug@
+// For this block to work, you must have
+// `mkbuildoptglobals.extra_flags={build.debug_port}` in `platform.local.txt`
+// Or move contents to the block with the signature "@create-file:build.opt@"
+
+
+// Removing the optimization for "sibling and tail recursive calls"  will clear
+// up some gaps in the stack decoder report. Preserves stack frames created at
+// each level as you call down to the next.
+-fno-optimize-sibling-calls
+
+
+// Adds a pointer toward the end of the stack frame that points to the beginning
+// of the stack frame. The stack dump will annotate the line where it occurs
+// with a `<` mark.
+-fno-omit-frame-pointer
+
+
+// Options for HWDT Stack Dump (hwdt_app_entry.cpp)
+
+// Alter the UART serial speed used for printing the Hardware WDT reset stack
+// dump. Without this option on an HWDT reset, the existing default speed of
+// 115200 bps will be used. If you are using this default speed, you can skip
+// this option. Note this option only changes the speed while the stack dump is
+// printing. Prior settings are restored.
+// -DDEBUG_ESP_HWDT_UART_SPEED=19200
+// -DDEBUG_ESP_HWDT_UART_SPEED=74880
+// -DDEBUG_ESP_HWDT_UART_SPEED=115200
+// -DDEBUG_ESP_HWDT_UART_SPEED=230400
+
+// HWDT Stack Dump defaults to print a simple introduction to let you know the
+// tool is active and in the build. At power-on, this may not be viewable on
+// some devices. Use the DEBUG_ESP_HWDT_UART_SPEED option above to improve.
+// Or uncomment line below to turn off greeting
+// -DDEBUG_ESP_HWDT_PRINT_GREETING=0
+
+// Demos
+-DDEMO_THUNK=1
+// -DDEMO_NOEXTRA4K=1
+-DDEMO_WIFI=1
+*/
+
+/*@create-file:build.opt@
+// -fno-optimize-sibling-calls
+// -fno-omit-frame-pointer
+
+// Demos
+-DDEMO_THUNK=1
+// -DDEMO_NOEXTRA4K=1
+-DDEMO_WIFI=1
+*/