Merge bitcoin/bitcoin#30840: docs: Updated debug build instructions for cmake

0b003e1 docs: Updated debug build instructions for cmake (ion-)

Pull request description:

  In the [developer notes](https://github.com/bitcoin/bitcoin/blob/master/doc/developer-notes.md) the section on [compiling for debug](https://github.com/bitcoin/bitcoin/blob/master/doc/developer-notes.md#compiling-for-debugging) displays outdated instructions that were applicable before the move to cmake build system.

  This PR just gives instructions on how to build for debugging in the context of cmake.

ACKs for top commit:
  kevkevinpal:
    ACK [0b003e1](bitcoin/bitcoin@0b003e1)
  achow101:
    ACK 0b003e1
  tdb3:
    ACK 0b003e1

Tree-SHA512: fc8b4824d68e47b3e64320b4ce728df4242d00c2e8c75dcf5daa60af3050c62d94fa9741e447c7d81e72194470ed68a4e19bbee8cf6a1412d6566c7b699cf242

Author: achow101

doc/developer-notes.md

@@ -354,8 +354,14 @@ Development tips and tricks
 
 ### Compiling for debugging
 
-Run configure with `--enable-debug` to add additional compiler flags that
-produce better debugging builds.
+When using the default build configuration by running `cmake -B build`, the
+`-DCMAKE_BUILD_TYPE` is set to `RelWithDebInfo`. This option adds debug symbols
+but also performs some compiler optimizations that may make debugging trickier
+as the code may not correspond directly to the source.
+
+If you need to build exclusively for debugging, set the `-DCMAKE_BUILD_TYPE`
+to `Debug` (i.e. `-DCMAKE_BUILD_TYPE=Debug`). You can always check the cmake
+build options of an existing build with `ccmake build`.
 
 ### Show sources in debugging