scripts: gen_compile_commands: fix invalid escape sequence warning

Since Python 3.12 unrecognised escape sequences trigger a SyntaxWarning.
Convert the '\#' string to a raw string so the backslash is correctly
used as a literal.

Ported from Linux commit dae4a0171e25 ("gen_compile_commands: fix invalid
escape sequence warning").

This updates the script to be in-line with Linux 6.9-rc6.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
Reviewed-by: João Marcos Costa <jmcosta944@gmail.com>
diff --git a/scripts/gen_compile_commands.py b/scripts/gen_compile_commands.py
index fec513e..e746add 100755
--- a/scripts/gen_compile_commands.py
+++ b/scripts/gen_compile_commands.py
@@ -172,7 +172,7 @@
     # escape the pound sign '#', either as '\#' or '$(pound)' (depending on the
     # kernel version). The compile_commands.json file is not interepreted
     # by Make, so this code replaces the escaped version with '#'.
-    prefix = command_prefix.replace('\#', '#').replace('$(pound)', '#')
+    prefix = command_prefix.replace(r'\#', '#').replace('$(pound)', '#')
 
     # Return the canonical path, eliminating any symbolic links encountered in the path.
     abs_path = os.path.realpath(os.path.join(root_directory, file_path))