docs: update install readme

- Give a hint on how to troubleshoot the contribs build.
- Add instruction for debugging runtime crashes using GDB.

Change-Id: I6ad931223ce0904fb292a59090d37a2cec422ae8

INSTALL.md

@@ -343,9 +343,24 @@ Built client could be find in `build/Jami`
 
 - These environment variables will be temporarily set when using build-windows.py to run tests.
 
+## Troubleshooting
+
+Build errors may occur if daemon dependencies have been updated since the last build, as the script may not fully detect or rebuild them in the correct order. For the same reason, you may also occasionally encounter linker errors.
+
+To resolve this, clean and restart the installation to ensure a fresh rebuild of all components (delete all temporary files generated by the build process):
+
+```bash
+./build.py --clean
+./build.py --install
+```
+
 ## Debugging
 
-Compile the client with with `-DCMAKE_BUILD_TYPE=Debug`.
+Compile the client with `-DCMAKE_BUILD_TYPE=Debug`. Then, if you want to enable logging when running `jami`, launch it with `-d` or `--debug`.
+
+To diagnose a crash, use GDB:
 
-Then, if you want to enable logging when running `jami`, launch it
-with `-d` or `--debug`.
+```sh
+./build.py --install --debug
+gdb -ex run --args ./jami --debug
+```