[docs] Document MODM_DEBUG_BUILD macro behavior

Author: salkinium

src/modm/architecture/detect.hpp

@@ -84,6 +84,9 @@
 /// Size of pointer in bytes
 #define	MODM_SIZEOF_POINTER
 
+/// Only defined in debug profile
+#define MODM_DEBUG_BUILD
+
 /// @}
 
 #else // !__DOXYGEN__

src/modm/architecture/interface/assert.md

@@ -175,6 +175,26 @@ just as above:
 4. `bool modm_assert_continue_fail_debug()`
 5. `bool modm_assert_continue_ignore_debug()`
 
+Alternatively, you can guard the entire assertion statement with the
+`MODM_BUILD_DEBUG` macro if you only want to execute the check and branch in
+debug profile:
+
+```cpp
+// The check is always performed, but only raises an assertion in debug profile!
+if (not modm_assert_continue_ignore_debug(cond, ...))
+{
+    // if the check fails, this branch is executed in release profile too!
+}
+
+#ifdef MODM_DEBUG_BUILD
+// This check if only performed in debug profile
+if (not modm_assert_continue_ignore(cond, ...))
+{
+    // if the check fails, this branch is executed only in debug profile!
+}
+#endif
+```
+
 
 ### When to use what?
 

tools/build_script_generator/module.md

@@ -36,6 +36,8 @@ For *release builds*:
 For *debug builds*:
 
 - `-Og`: optimize for debugging experience.
+- `MODM_DEBUG_BUILD`: this macro is only defined in debug profile. You can use
+                      it with `#ifdef MODM_DEBUG_BUILD` to enable debug code.
 
 #### Only C